- --------------------------------------------------------------------------------


                            NORTHWESTERN CORPORATION


                                       TO


                              THE BANK OF NEW YORK


                                       AND


                                MARYBETH LEWICKI


                         As Trustees under Mortgage and
                           Deed of Trust, dated as of
                 October 1, 1945, with NorthWestern Corporation


                               -----------------


                       TWENTY-THIRD SUPPLEMENTAL INDENTURE

                       Providing, among other things, for

            the succession of MaryBeth Lewicki to Douglas J. MacInnes
               as Co-Trustee under such Mortgage and Deed of Trust

                                       and

         First Mortgage Bonds, Credit Agreement (2002) Series, due 2006


                               -----------------


                          Dated as of February 1, 2003




- --------------------------------------------------------------------------------










                       TWENTY-THIRD SUPPLEMENTAL INDENTURE

                                 --------------

                  THIS TWENTY-THIRD SUPPLEMENTAL INDENTURE, dated as of February
1, 2003, between NORTHWESTERN  CORPORATION,  a corporation duly incorporated and
existing  under  the  laws of the  State of  Delaware  (hereinafter  called  the
"Company"),  having its principal  office at 125 S. Dakota  Avenue,  Suite 1100,
Sioux Falls,  South Dakota 57104, and THE BANK OF NEW YORK  (hereinafter  called
the  "Corporate  Trustee"),  a  corporation  of the  State  of New  York,  whose
principal corporate trust office is located at 101 Barclay Street, New York, New
York 10286  (successor to MORGAN  GUARANTY  TRUST COMPANY OF NEW YORK  (formerly
Guaranty Trust Company of New York)),  and MARYBETH  LEWICKI,  whose post office
address is c/o The Bank of New York,  101  Barclay  Street,  New York,  New York
10286,  who hereby is  appointed  successor  Co-Trustee  to Douglas J.  MacInnes
(successor to Arthur E. Burke,  Karl R. Henrich,  H.H. Gould, R. Amundsen,  P.J.
Crowley and W.T. Cunningham) (said MaryBeth Lewicki being hereinafter  sometimes
called the  "Co-Trustee",  and the Corporate  Trustee and the  Co-Trustee  being
hereinafter  together  sometimes called the  "Trustees"),  as Trustees under the
Mortgage and Deed of Trust, dated as of October 1, 1945 (hereinafter  called the
"Mortgage"  and,  together  with  any  indentures   supplemental   thereto,  the
"Indenture"),  which  Mortgage was executed and  delivered by The Montana  Power
Company,  a  corporation  of the State of New  Jersey  (hereinafter  called  the
"Company-New Jersey"), as indirect predecessor under the Mortgage to the Company
(the Company being successor under the Mortgage to NorthWestern  Energy,  L.L.C.
(hereinafter called "NorthWestern Energy"), formerly known as The Montana Power,
L.L.C., a limited  liability  company of the State of Montana,  and NorthWestern
Energy being the successor  under the Mortgage to The Montana Power  Company,  a
corporation of the State of Montana (hereinafter called the "Company-Montana")),
to Guaranty  Trust  Company of New York and Arthur E.  Burke,  as  Trustees,  to
secure the payment of bonds issued or to be issued under and in accordance  with
the provisions of the Mortgage, reference to which Mortgage is hereby made, this
instrument (hereinafter called the "Twenty-third  Supplemental Indenture") being
supplemental thereto;

                  WHEREAS,  by the Mortgage,  the Company-New  Jersey covenanted
that it would execute and deliver such supplemental  indenture or indentures and
such  further  instruments  and do such  further  acts as might be  necessary or
proper to carry out more  effectually  the purposes of the Indenture and to make
subject to the lien of the Indenture any property thereafter  acquired,  made or
constructed and intended to be subject to the lien thereof; and

                  WHEREAS,  the Company-New Jersey executed and delivered to the
Trustees its First Supplemental Indenture,  dated as of May 1, 1954 (hereinafter
called  the  "First  Supplemental  Indenture"),   and  its  Second  Supplemental
Indenture,   dated  as  of  April  1,  1959  (hereinafter   called  the  "Second
Supplemental Indenture"); and




                  WHEREAS,   the   Company-New   Jersey  was  merged   into  the
Company-Montana  on November 30, 1961,  and to evidence  the  succession  of the
Company-Montana  to the  Company-New  Jersey for  purposes  of the bonds and the
Indenture  and  the  assumption  by the  Company-Montana  of the  covenants  and
conditions of the Company-New Jersey in the bonds and in the Indenture contained
and to enable the  Company-Montana to have and exercise the powers and rights of
the Company-New Jersey under the Indenture in accordance with the terms thereof,
the   Company-Montana   executed  and   delivered  to  the  Trustees  its  Third
Supplemental  Indenture,  dated as of November 30, 1961 (hereinafter  called the
"Third Supplemental Indenture"); and

                  WHEREAS,  the  Company-Montana  executed and  delivered to the
Trustees  its  Fourth  Supplemental  Indenture,   dated  as  of  April  1,  1970
(hereinafter called the "Fourth Supplemental Indenture"); its Fifth Supplemental
Indenture, dated as of April 1, 1971 (hereinafter called the "Fifth Supplemental
Indenture");  its  Sixth  Supplemental  Indenture,  dated as of  March  1,  1974
(hereinafter   called  the  "Sixth   Supplemental   Indenture");   its   Seventh
Supplemental  Indenture,  dated as of December 1, 1974  (hereinafter  called the
"Seventh Supplemental Indenture");  its Eighth Supplemental Indenture,  dated as
of July 1, 1975 (hereinafter called the "Eighth  Supplemental  Indenture");  its
Ninth Supplemental  Indenture,  dated as of December 1, 1975 (hereinafter called
the "Ninth Supplemental Indenture");  its Tenth Supplemental Indenture, dated as
of January 1, 1979 (hereinafter called the "Tenth Supplemental Indenture");  its
Eleventh Supplemental Indenture, dated as of October 1, 1983 (hereinafter called
the "Eleventh  Supplemental  Indenture");  its Twelfth  Supplemental  Indenture,
dated as of  January  1, 1984  (hereinafter  called  the  "Twelfth  Supplemental
Indenture"); its Thirteenth Supplemental Indenture, dated as of December 1, 1991
(hereinafter  called the "Thirteenth  Supplemental  Indenture");  its Fourteenth
Supplemental  Indenture,  dated as of  January 1, 1993  (hereinafter  called the
"Fourteenth  Supplemental  Indenture");  its Fifteenth  Supplemental  Indenture,
dated  as of March 1,  1993  (hereinafter  called  the  "Fifteenth  Supplemental
Indenture");  its  Sixteenth  Supplemental  Indenture,  dated as of May 1,  1993
(hereinafter  called the "Sixteenth  Supplemental  Indenture");  its Seventeenth
Supplemental  Indenture,  dated as of December 1, 1993  (hereinafter  called the
"Seventeenth  Supplemental  Indenture");  its Eighteenth Supplemental Indenture,
dated as of August 5, 1994  (hereinafter  called  the  "Eighteenth  Supplemental
Indenture");  its Nineteenth  Supplemental  Indenture,  dated as of December 16,
1999  (hereinafter  called the  "Nineteenth  Supplemental  Indenture");  and its
Twentieth  Supplemental  Indenture,  dated as of November  1, 2001  (hereinafter
called the "Twentieth Supplemental Indenture"); and

                  WHEREAS,  the  Company-Montana  was merged  into  NorthWestern
Energy (under its then name,  The Montana  Power,  L.L.C.) on February 13, 2002,
and to evidence the succession of NorthWestern  Energy (under its then name, The
Montana Power,  L.L.C.) to the Company-Montana for purposes of the bonds and the
Indenture and the  assumption by  NorthWestern  Energy (under its then name, The
Montana Power, L.L.C.) of the covenants and conditions of the Company-Montana in
the bonds and in the  Indenture  contained  and to  enable  NorthWestern  Energy
(under its then name, The Montana Power, L.L.C.) to have and exercise the powers
and rights of the  Company-Montana  under the Indenture in  accordance

                                       2



with the terms  thereof,  NorthWestern  Energy (under its then name, The Montana
Power,   L.L.C.)  executed  and  delivered  to  the  Trustees  its  Twenty-First
Supplemental  Indenture,  dated as of February 13, 2002 (hereinafter  called the
"Twenty-first Supplemental Indenture"); and

                  WHEREAS, NorthWestern Energy changed its name from The Montana
Power, L.L.C. to NorthWestern Energy, L.L.C. on March 19, 2002; and

                  WHEREAS, NorthWestern Energy transferred,  subject to the Lien
of the Indenture,  substantially all of the Mortgaged and Pledged Property as an
entirety to the  Company on November  20,  2002 (the  "Transfer  Date"),  and to
evidence the  succession of the Company to  NorthWestern  Energy for purposes of
the bonds and the Indenture  and the  assumption by the Company of the covenants
and  conditions  of  NorthWestern  Energy  in the  bonds  and  in the  Indenture
contained  and to enable the Company to have and  exercise the powers and rights
of NorthWestern Energy under the Indenture in accordance with the terms thereof,
the  Company   executed  and   delivered  to  the  Trustees  its   Twenty-second
Supplemental  Indenture,  dated as of November 15, 2002 (hereinafter  called the
"Twenty-second Supplemental Indenture"); and

                  WHEREAS,  the Mortgage and the First,  Second,  Third, Fourth,
Fifth, Sixth, Seventh,  Eighth,  Ninth, Tenth,  Eleventh,  Twelfth,  Thirteenth,
Fourteenth,   Fifteenth,   Sixteenth,   Seventeenth,   Eighteenth,   Nineteenth,
Twentieth,  Twenty-first and Twenty-second Supplemental Indentures were recorded
in the  official  records of various  counties  and  states as  required  by the
Indenture; and

                  WHEREAS,  an  instrument  dated March 15, 1955 was executed by
the Company-New Jersey appointing Karl R. Henrich as Co-Trustee in succession to
said  Arthur E.  Burke,  resigned,  under the  Mortgage  and by Karl R.  Henrich
accepting the appointment as Co-Trustee under the Mortgage in succession to said
Arthur E. Burke, which instrument was recorded in various counties in the states
of Montana, Idaho and Wyoming; and

                  WHEREAS, an instrument dated June 29, 1962 was executed by the
Company-Montana  appointing  H.H. Gould as Co-Trustee in succession to said Karl
R.  Henrich,  resigned,  under the  Mortgage  and by H.H.  Gould  accepting  the
appointment  as  Co-Trustee  under the  Mortgage in  succession  to said Karl R.
Henrich,  which  instrument  was  recorded in various  counties in the states of
Montana, Idaho and Wyoming; and

                  WHEREAS, an instrument dated June 22, 1973 was executed by the
Company-Montana  appointing R. Amundsen as Co-Trustee in succession to said H.H.
Gould, resigned, under the Mortgage and by R. Amundsen accepting the appointment
as  Co-Trustee  under the  Mortgage  in  succession  to said H.H.  Gould,  which
instrument was recorded in various counties in the states of Montana,  Idaho and
Wyoming; and

                  WHEREAS,  an instrument dated July 1, 1986 was executed by the
Company-Montana  appointing P.J.  Crowley as Co-Trustee in succession to said R.
Amundsen,  resigned,  under  the  Mortgage  and by  P.J  Crowley  accepting  the
appointment as Co-Trustee

                                       3


under the Mortgage in  succession  to said R.  Amundsen,  which  instrument  was
recorded in various counties in the states of Montana, Idaho and Wyoming; and

                  WHEREAS,  by  the  Eighteenth  Supplemental   Indenture,   the
Company-Montana  appointed  (i) W.T.  Cunningham  as Co-Trustee in succession to
said P.J. Crowley, resigned, under the Mortgage and W.T. Cunningham accepted the
appointment as Co-Trustee under the Mortgage in succession to said P.J. Crowley,
and (ii) The Bank of New York as  Corporate  Trustee  in  succession  to  Morgan
Guaranty Trust Company of New York, resigned, under the Mortgage and The Bank of
New York  accepted the  appointment  as Corporate  Trustee under the Mortgage in
succession to said Morgan Guaranty Trust Company of New York, which supplemental
indenture was recorded in various  counties in the states of Montana,  Idaho and
Wyoming; and

                  WHEREAS,  an  instrument  dated March 29, 1999 was executed by
the  Company-Montana  appointing Douglas J. MacInnes as Co-Trustee in succession
to said W.T. Cunningham, resigned, under the Mortgage and by Douglas J. MacInnes
accepting the appointment as Co-Trustee under the Mortgage in succession to said
W.T. Cunningham, which instrument was recorded in various counties in the states
of Montana, Idaho and Wyoming; and

                  WHEREAS,  as  permitted  by Section 101 and Section 102 of the
Mortgage  (as  heretofore  supplemented),  and  there  being no  Default  and no
occurrence of an event which,  after notice, the passage of time, or both, would
constitute  a Default,  the  Company  desires to remove  Douglas J.  MacInnes as
Co-Trustee  under the  Mortgage  and to appoint  MaryBeth  Lewicki as  successor
Co-Trustee under the Mortgage,  subject to the conditions of Article XVII of the
Mortgage,  effective  as of the close of business on February 7, 2003,  and said
MaryBeth Lewicki desires to accept such  appointment,  effective as of the close
of business on February  7, 2003,  in each case,  pursuant to this  Twenty-third
Supplemental Indenture;

                  WHEREAS,  the Company-New  Jersey or the  Company-Montana  has
heretofore  issued,  in accordance  with the  provisions  of the  Mortgage,  the
following series of First Mortgage Bonds:




                                                                         Principal
                                                                          Amount             Principal Amount
                           Series                                         Issued               Outstanding
                           ------                                         ------               -----------

                                                                                         
2-7/8% Series due 1975 ...................................             $40,000,000                NONE
3-1/8% Series due 1984 ...................................               6,000,000                NONE
4-1/2% Series due 1989 ...................................              15,000,000                NONE
8-1/4% Series due 1974 ...................................              30,000,000                NONE
7-1/2% Series due 2001 (Fifth)............................              25,000,000                NONE
8-5/8% Series due 2004....................................              60,000,000                NONE
8-3/4% Series due 1981....................................              30,000,000                NONE
9.60% Series due 2005.....................................              35,000,000                NONE
9.70% Series due 2005.....................................              65,000,000                NONE



                                       4




                                                                         Principal
                                                                          Amount             Principal Amount
                           Series                                         Issued               Outstanding
                           ------                                         ------               -----------

                                                                                         
9-7/8% Series due 2009....................................              50,000,000                NONE
11-3/4% Series due 1993...................................              75,000,000                NONE
10/10-1/8% Series due 2004/2014...........................              80,000,000                NONE
8-1/8% Series due 2014....................................              41,200,000                NONE
7.70% Series due 1999 (Fourteenth)........................              55,000,000                NONE
8-1/4% Series due 2007 (Fifteenth)........................              55,000,000                $365,000
8.95% Series 2022 (Sixteenth).............................              50,000,000               1,466,000
Secured Medium-Term Notes (Seventeenth)...................              68,000,000              13,000,000
7% Series due 2005 (Eighteenth)...........................              50,000,000               5,386,000
6-1/8% Series due 2023 (Nineteenth).......................              90,205,000              90,205,000
5.90% Series due 2023 (Twentieth).........................              80,000,000              80,000,000
0% Series due 1999 (Twenty-first).........................             210,321,007                NONE
7.30% Series due 2006 (Twenty-second).....................             150,000,000             150,000,000


which bonds are also  hereinafter  sometimes  called "Bonds of the First through
Twenty-second Series", respectively; and


                  WHEREAS,  Section 8 of the Mortgage  provides that the form of
each series of bonds (other than the First Series) issued  thereunder and of the
coupons to be attached to coupon  bonds of such series shall be  established  by
Resolution  of the Board of  Directors  of the Company and that the form of such
series, as established by said Board of Directors, shall specify the descriptive
title of the bonds and various  other terms  thereof,  and may also contain such
provisions not inconsistent with the provisions of the Indenture as the Board of
Directors may, in its  discretion,  cause to be inserted  therein  expressing or
referring  to the terms and  conditions  upon  which such bonds are to be issued
and/or secured under the Indenture; and

                  WHEREAS,  Section 120 of the  Mortgage  provides,  among other
things, that any power, privilege or right expressly or impliedly reserved to or
in any way conferred upon the Company by any provision of the Indenture, whether
such power, privilege or right is in any way restricted or is unrestricted,  may
be in whole or in part waived or surrendered or subjected to any  restriction if
at the time unrestricted or to additional restriction if already restricted, and
the Company may enter into any further  covenants,  limitations or  restrictions
for the benefit of any one or more  series of bonds  issued  thereunder,  or the
Company  may  cure  any  ambiguity  contained  therein  or in  any  supplemental
indenture or may (in lieu of  establishment by Resolution as provided in Section
8 of the  Mortgage)  establish  the terms and  provisions of any series of bonds
other  than  the  First  Series,  by  an  instrument  in  writing  executed  and
acknowledged  by the Company in such manner as would be  necessary  to entitle a
conveyance  of real estate to record in all of the states in which any  property
at the time subject to the lien of the Indenture shall be situated; and

                  WHEREAS,  the  Company  now  desires to create a new series of
bonds and (pursuant to the  provisions of Section 120 of the Mortgage) to add to
its covenants and agreements  contained in the Mortgage  certain other covenants
and  agreements to be observed by it and to alter and amend in certain  respects
the covenants and provisions contained in the Indenture; and



                                       5


                  WHEREAS,  the  execution  and  delivery by the Company of this
Twenty-third  Supplemental  Indenture,  and  the  terms  of  the  Bonds  of  the
Twenty-third  Series,  hereinafter referred to, have been duly authorized by the
Board of Directors of the Company by  appropriate  Resolutions  of said Board of
Directors.

                  NOW, THEREFORE, THIS INDENTURE WITNESSETH:

                  That the Company,  pursuant to Section 101 of the Mortgage (as
heretofore supplemented), and by order of its Board of Directors, hereby removes
Douglas J. MacInnes as  Co-Trustee  under the Mortgage (and will furnish to said
Douglas J. MacInnes a manually signed original of this Supplemental Indenture as
an instrument of such removal) effective as of the close of business on February
7, 2003;

                  That,  pursuant to Section 102 of the Mortgage (as  heretofore
supplemented),  and by  order of its  Board of  Directors,  the  Company  hereby
appoints MaryBeth Lewicki as successor Co-Trustee under the Mortgage, subject to
the conditions of Article XVII thereof, effective as of the close of business on
February 7, 2003;

                  That the undersigned MaryBeth Lewicki, a citizen of the United
States of America,  hereby  accepts her  appointment by the Company as successor
Co-Trustee  under the Mortgage  (and,  pursuant to Section 104 of the  Mortgage,
will  furnish to said  Douglas J.  MacInnes  and the  Company a manually  signed
original of this  Supplemental  Indenture as an instrument  of such  acceptance)
effective as of the close of business on February 7, 2003;

                  That the Company  will  proceed  with the  publication  of the
notice of the aforesaid removal and the notice of the aforesaid appointment,  as
required,  respectively,  by Section  101 and Section  102 of the  Mortgage  (as
heretofore supplemented), in substantially the forms provided,  respectively, in
Exhibit A-1 and Exhibit A-2 attached hereto;

                  That the  Company,  in  consideration  of the  premises and of
$1.00 to it duly paid by the Trustees at or before the ensealing and delivery of
these  presents,  the  receipt  whereof is hereby  acknowledged,  and in further
evidence of  assurance  of the estate,  title and rights of the  Trustees and in
order  further to secure the payment of both the  principal  of and interest and
premium,  if any,  on the bonds from time to time  issued  under the  Indenture,
according to their tenor and effect and the performance of all the provisions of
the Indenture  (including any modification made as in the Mortgage provided) and
of  said  bonds,  and to  confirm  the  lien  of  the  Mortgage,  as  heretofore
supplemented,  on certain  after-acquired  property,  hereby  grants,  bargains,
sells, releases, conveys, assigns, transfers,  mortgages, pledges, sets over and
confirms (subject,  however, to Excepted Encumbrances as defined in Section 6 of
the Mortgage, as heretofore supplemented) unto Douglas J. MacInnes, who is being
removed as Co-Trustee effective as of the close of business on February 7, 2003,
and to MaryBeth Lewicki, who is being appointed as Co-Trustee and accepting such
appointment  as Co-Trustee  effective as of the close of business on February 7,
2003, and (to the extent of its legal capacity to hold the same for the purposes
hereof) to The Bank of New York,  the Corporate  Trustee,  as Trustees under the
Indenture,  and to their  successor  or  successors  in said trust,  and to said
Trustees and their successors and assigns forever, all property, real,


                                       6


personal  and  mixed,  of the  kind  or  nature  specifically  mentioned  in the
Mortgage, as heretofore supplemented, or of any other kind or nature (whether or
not located in the State of Montana),  acquired by the Company after the date of
the execution and delivery of the Mortgage,  as heretofore  supplemented (except
any herein or in the Mortgage, as heretofore supplemented,  expressly excepted),
now owned or,  subject to the  provisions of subsection (I) of Section 87 of the
Mortgage,  as  heretofore  supplemented,  hereafter  acquired by the Company (by
purchase,  consolidation,  merger,  donation,  construction,  erection or in any
other way) and wheresoever  situated,  including (without in anywise limiting or
impairing by the  enumeration of the same the scope and intent of the foregoing,
or of any general  description  contained  in the  Indenture)  all lands,  power
sites,  flowage rights,  water rights,  water locations,  water  appropriations,
ditches, flumes, reservoirs, reservoir sites, canals, raceways, dams, dam sites,
aqueducts and all other rights or means for  appropriating,  conveying,  storing
and supplying  water; all rights of way and roads; all plants for the generation
of electricity by steam, water and/or other power; all powerhouses,  gas plants,
street  lighting  systems,  standards and other  equipment  incidental  thereto,
telephone, radio and television systems,  air-conditioning systems and equipment
incidental thereto, water works, water systems, steam heat and hot water plants,
substations,  lines, service and supply systems, bridges,  culverts, tracks, ice
or refrigeration plants and equipment,  offices,  buildings and other structures
and the equipment thereof, all machinery,  engines, boilers, dynamos,  electric,
gas and other machines,  regulators,  meters, transformers,  generators, motors,
electrical, gas and mechanical appliances,  conduits, cables, water, steam heat,
gas or other pipes,  gas mains and pipes,  service pipes,  fittings,  valves and
connections,  pole and transmission lines,  wires,  cables,  tools,  implements,
apparatus,  furniture and chattels;  all  franchises,  consents or permits,  all
lines for the transmission and distribution of electric current, gas, steam heat
or  water  for any  purpose  including  towers,  poles,  wires,  cables,  pipes,
conduits,  ducts and all  apparatus for use in  connection  therewith;  all real
estate, lands, easements, servitudes, licenses, permits, franchises, privileges,
rights of way and other rights in or relating to real estate or the occupancy of
the same and (except as herein or in the Mortgage,  as heretofore  supplemented,
expressly  excepted) all the right,  title and interest of the Company in and to
all other  property  of any kind or nature  appertaining  to and/or  used and/or
occupied and/or enjoyed in connection  with any property  hereinbefore or in the
Mortgage, as heretofore supplemented, described.

                  TOGETHER with all and singular the  tenements,  hereditaments,
prescriptions, servitudes and appurtenances belonging or in anywise appertaining
to  the  aforesaid  property  or  any  part  thereof,  with  the  reversion  and
reversions,  remainder and  remainders and (subject to the provisions of Section
57 of the  Mortgage)  the tolls,  rents,  revenues,  issues,  earnings,  income,
product and profits thereof,  and all the estate,  right, title and interest and
claim whatsoever,  at law as well as in equity, which the Company now has or may
hereafter acquire in and to the aforesaid property and franchises and every part
and parcel thereof.

                  IT IS  HEREBY  AGREED  by the  Company  that,  subject  to the
provisions  of  subsection  (I) of Section  87 of the  Mortgage,  as  heretofore
supplemented,  all the property,  rights and franchises  acquired by the Company
(by purchase, consolidation,  merger,


                                       7


donation,  construction,  erection  or in any other way) after the date  hereof,
except any herein or in the  Mortgage,  as  heretofore  supplemented,  expressly
excepted,  shall be and are as fully  granted and  conveyed  hereby and as fully
embraced  within the lien  hereof and the lien of the  Mortgage,  as  heretofore
supplemented,  as if such property,  rights and franchises were now owned by the
Company and were specifically described herein and conveyed hereby.

                  PROVIDED that the following are not and are not intended to be
now  or  hereafter  granted,  bargained,  sold,  released,  conveyed,  assigned,
transferred,  mortgaged, hypothecated,  affected, pledged, set over or confirmed
hereunder and are hereby  expressly  excepted from the lien and operation of the
Mortgage,  as supplemented,  viz: (1) cash,  shares of stock,  bonds,  notes and
other  obligations  and  other  securities  not  specifically   pledged,   paid,
deposited,  delivered or held under the Mortgage, as supplemented, or covenanted
so to be; (2) merchandise,  equipment, apparatus, materials or supplies held for
the purpose of sale or other disposition in the usual course of business;  fuel,
oil and similar materials and supplies consumable in the operation of any of the
properties  of the Company;  all  aircraft,  tractors,  rolling  stock,  trolley
coaches, buses, motor coaches, automobiles, motor trucks, and other vehicles and
materials  and supplies held for the purpose of repairing or replacing (in whole
or part) any of the same; (3) bills, notes and accounts  receivable,  judgments,
demands and choses in action, and all contracts, leases and operating agreements
not specifically pledged under the Mortgage,  as supplemented,  or covenanted so
to be; the Company's  contractual rights or other interest in or with respect to
tires  not  owned by the  Company;  (4) the last day of the term of any lease or
leasehold  which  may be or  become  subject  to the  lien of the  Mortgage,  as
supplemented;  (5) electric energy,  gas, steam, water, ice, and other materials
or products  generated,  manufactured,  produced,  purchased  or acquired by the
Company for sale,  distribution  or use in the ordinary  course of its business;
all  timber,  minerals,  mineral  rights  and  royalties  and  all  Gas  and Oil
Production Property,  as defined in Section 4 of the Mortgage,  as supplemented;
(6) the Company's franchise to be a corporation; and (7) any property heretofore
released pursuant to any provisions of the Indenture and not heretofore disposed
of by the Company-New  Jersey, the  Company-Montana,  NorthWestern Energy or the
Company; provided, however, that the property and rights expressly excepted from
the  lien  and  operation  of  the  Mortgage,  as  supplemented,  in  the  above
subdivisions  (2) and (3) shall (to the extent  permitted by law) cease to be so
excepted in the event and as of the date that either or both of the  Trustees or
a receiver or trustee shall enter upon and take  possession of the Mortgaged and
Pledged  Property  in the manner  provided  in Article  XIII of the  Mortgage by
reason of the occurrence of a Default as defined in Section 65 thereof.

                  TO HAVE AND TO HOLD all such  properties,  real,  personal and
mixed, granted,  bargained,  sold, released,  conveyed,  assigned,  transferred,
mortgaged,  pledged,  set over or  confirmed  by the  Company as  aforesaid,  or
intended so to be, unto the  Co-Trustee and (to the extent of its legal capacity
to hold  the same for the  purposes  hereto)  unto  the  Corporate  Trustee,  as
Trustees, and their successors and assigns forever.

                  IN TRUST NEVERTHELESS, for the same purposes and upon the same
terms,  trusts and  conditions  and  subject to and with the same  provisos  and
covenants as are


                                       8


set forth in the  Mortgage,  as  supplemented,  this  Twenty-third  Supplemental
Indenture being supplemental thereto.

                  AND IT IS HEREBY COVENANTED by the Company that all the terms,
conditions,  provisos,  covenants and provisions  contained in the Mortgage,  as
supplemented,  shall affect and apply to the property hereinbefore described and
conveyed and to the estate,  rights,  obligations  and duties of the Company and
the Trustees and the  beneficiaries  of the trust with respect to said property,
and to the Trustees  and their  successors  as Trustees of said  property in the
same manner and with the same effect as if the said  property  had been owned by
the  Company-New  Jersey at the time of the execution of the  Mortgage,  and had
been  specifically and at length  described in and conveyed to the Trustees,  by
the Mortgage as a part of the property therein stated to be conveyed.

                  SUBJECT   NEVERTHELESS,   to  the   limitation   permitted  by
subsection  (I) of Section 87 of the Mortgage,  as  supplemented,  namely,  that
notwithstanding the foregoing,  the Mortgage, as supplemented,  shall not become
or be or be  required  to  become  or be a lien  upon any of the  properties  or
franchises  owned by the Company on the Transfer Date or thereafter  acquired by
the  Company  (by  purchase,  consolidation,   merger,  donation,  construction,
erection or in any other way) except (a) those acquired by it from  NorthWestern
Energy,  and  improvements,  extensions  and additions  thereto and renewals and
replacements thereof, (b) the property made and used by the Company as the basis
under any of the provisions of the Indenture for the authentication and delivery
of  additional  bonds or the  withdrawal of cash or the release of property or a
credit under Section 39 or Section 40 of the Indenture, and (c) such franchises,
repairs and additional  property as may be acquired,  made or constructed by the
Company  (1) to  maintain,  renew and  preserve  the  franchises  covered by the
Indenture,  or (2)  to  maintain  the  property  mortgaged  and  intended  to be
mortgaged under the Indenture as an operating  system or systems in good repair,
working  order and  condition,  or (3) in  rebuilding  or renewal  of  property,
subject  to the Lien  under  the  Indenture,  damaged  or  destroyed,  or (4) in
replacement of or  substitution  for machinery,  apparatus,  equipment,  frames,
towers, poles, wire, pipe, tools, implements and furniture,  subject to the Lien
thereunder, which shall have become old, inadequate,  obsolete, worn out, unfit,
unadapted, unserviceable, undesirable or unnecessary for use in the operation of
the property mortgaged and intended to be mortgaged thereunder.

                  The  Company  further  covenants  and  agrees  to and with the
Trustees and their successors in said trust under the Indenture, as follows:

                                   ARTICLE I

                          Twenty-third Series of Bonds

                  Section  1.1  There  shall  be a series  of  bonds  designated
"Credit  Agreement  (2002)  Series,  due 2006"  (such  series  herein  sometimes
referred to as the  "Twenty-third  Series"  and the bonds of such series  herein
sometimes  referred to as the "Bonds of the Twenty-third  Series") each of which
shall  also bear the  descriptive  title  "First  Mortgage  Bond",  and the form
thereof,  which as  established  by  Resolution of the Board of Directors of the
Company,


                                       9


shall be  substantially  as provided in Exhibit B attached hereto and,  thereby,
shall contain  suitable  provisions  with respect to the matters  hereinafter in
this Section specified.

                  Bonds of the  Twenty-third  Series  shall be  issued to Credit
Suisse First Boston,  acting  through its Cayman Islands  Branch,  as collateral
agent (together with its successors in such capacity,  the  "Collateral  Agent")
under the Bond Collateral  Agreement,  dated as of February 10, 2003 (as amended
or otherwise  modified,  or as waived, or as replaced in each case, from time to
time in accordance  with its terms,  the  "Collateral  Agreement"),  between the
Company and the Collateral  Agent,  to secure the  obligations of the Company to
pay when due the Applicable  Share (as hereinafter  defined) of the principal of
and interest on the loans (the  "Loans") made and  outstanding  under the Credit
Agreement,  dated as of December 17, 2002 (as amended or otherwise modified,  or
as waived,  or as replaced,  in each case,  from time to time in accordance with
its terms, the "Credit Agreement"),  among the Company, as borrower, the several
lenders from time to time  parties  thereto (the  "Lenders")  and Credit  Suisse
First Boston,  acting through its Cayman Islands Branch, as administrative agent
(together with its successors in such capacity, the "Administrative Agent").

                  As used herein,  "Applicable  Share"  means,  as of any day, a
fraction  (expressed as a percentage  rounded to the eighth decimal place),  (i)
the  numerator of which is the  aggregate  principal  amount of the Bonds of the
Twenty-third  Series that are  Outstanding on such day, and (ii) the denominator
of which is the sum of (a) the  aggregate  principal  amount of the Bonds of the
Twenty-third  Series that are  Outstanding  on such day,  plus (b) the aggregate
principal amount of the New Mortgage Bonds,  Credit Agreement (2002) Series, due
2006,  of the Company  (the "South  Dakota  Credit  Agreement  Bonds")  that are
outstanding  on such day  under the  Company's  Mortgage  Indenture  and Deed of
Trust,  dated as of August 1, 1993,  relating  (among other  things) to property
owned by the  Company in the States of South  Dakota,  Nebraska,  Iowa and North
Dakota (as amended and supplemented,  the "South Dakota  Mortgage").  Initially,
the Applicable Share will be 71.79487179%  (being the expression as a percentage
(rounded to the eighth decimal  place) of a fraction,  the numerator of which is
$280,000,000  (the aggregate  principal  amount of the Bonds of the Twenty-third
Series  that are to be issued and become  Outstanding)  and the  denominator  of
which is $390,000,000 (the sum of $280,000,000,  the aggregate  principal amount
of the  Bonds of the  Twenty-third  Series  that  are to be  issued  and  become
Outstanding,  plus  $110,000,000,  the aggregate  principal  amount of the South
Dakota Credit Agreement Bonds that are to be issued and become outstanding under
the South Dakota Mortgage  simultaneously  with the issuance of the Bonds of the
Twenty-third Series). Pursuant to the Collateral Agreement, the Collateral Agent
will furnish to the  Corporate  Trustee  (with a copy to the Company) as soon as
practicable after any change in the Applicable Share, a certificate, signed by a
person  purporting to be its duly  authorized  officer,  notifying the Corporate
Trustee  of  such  change  in  the  Applicable   Share  (an  "Applicable   Share
Certificate"). Each Applicable Share Certificate shall set forth (i) the changed
Applicable  Share,  (ii) the date such  change  occurred,  (iii)  the  aggregate
principal amount of the Bonds of the Twenty-third  Series then Outstanding,  and
(iv) the aggregate  principal  amount of the South Dakota Credit Agreement Bonds
then  outstanding  under the South Dakota  Mortgage.  The Corporate  Trustee may
conclusively  presume that the Applicable Share is


                                       10


71.79487179% unless and until the Corporate Trustee receives an Applicable Share
Certificate.  Following  receipt by the Corporate Trustee of an Applicable Share
Certificate,  the Corporate Trustee may conclusively presume that the Applicable
Share is as set forth in such Applicable Share Certificate  unless and until the
Corporate  Trustee receives a subsequent  Applicable Share  Certificate (and the
Corporate Trustee shall be fully protected in relying thereon).

                  Bonds of the  Twenty-third  Series shall mature on December 1,
2006 (the "Maturity Date"), with an installment of the principal of the Bonds of
the Twenty-third Series in an amount equal to $700,000 (said amount representing
one quarter of one percent (0.25%) of the original aggregate principal amount of
the Bonds of the Twenty-third Series) being payable on the last Business Day (as
hereinafter defined) of each March, June, September and December occurring prior
to the  Maturity  Date,  commencing  March  31,  2003,  and the  balance  of the
principal of the Bonds of the Twenty-third  Series being payable on the Maturity
Date (in each case,  unless an equal  installment or balance of principal of the
Loans is not due and payable on such  Business Day or on the Maturity  Date,  as
applicable,  in  accordance  with  the  Credit  Agreement  by  reason  of  prior
prepayment  of the Loans (in which event,  there shall be due and payable on the
Bonds of the  Twenty-third  Series on such Business Day or on the Maturity Date,
as  applicable,  an amount of  principal  of said Bonds equal to the  Applicable
Share of the amount of principal  of the Loans that is payable on such  Business
Day or on the  Maturity  Date,  as  applicable,  in  accordance  with the Credit
Agreement));  they shall be issued as fully registered bonds in denominations of
One Thousand Dollars or in any integral  multiple of One Dollar in Excess of One
Thousand  Dollars;  the unpaid principal amount of the Bonds of the Twenty-third
Series  shall bear  interest at one or more  variable  interest  rates per annum
which  rate or rates  for each day shall be equal to the rate or rates per annum
borne  by the  Loans  in  accordance  with  the  Credit  Agreement  for such day
(calculated in the manner  provided in the Credit  Agreement for the calculation
of interest on the Loans),  payable on each day on which  interest is payable on
the Loans in accordance with the Credit Agreement (and in an amount equal to the
Applicable  Share of the amount of interest that is payable on the Loans on such
day in accordance  with the Credit  Agreement) to the Collateral  Agent,  as the
registered  owner,  without  regard to, or necessity  for, any record date;  the
principal  of and  interest  on each said Bond to be  payable  at the  office or
agency of the Company in the Borough of Manhattan, The City of New York, in such
coin or  currency  of the United  States of America as at the time of payment is
legal  tender for public and private  debts.  Bonds of the  Twenty-third  Series
shall  be dated as in  Section  10 of the  Mortgage  provided.  As used  herein,
"Business  Day" means a day other than a Saturday,  Sunday or other day on which
commercial banks in New York City are authorized or required by law to close.

                  For the  avoidance of any doubt,  it is expressly  stated that
scheduled  amortization  payments with respect to the Bonds of the  Twenty-third
Series  (as  specified  for the Bonds of the  Twenty-third  Series  prior to the
Maturity Date pursuant to the preceding paragraph of this Section 1.1) shall not
constitute  a  redemption  in part of the Bonds of the  Twenty-third  Series for
purposes  of Section  53 of the  Mortgage  (as  supplemented)  (and,  therefore,
surrender  of the Bonds of the  Twenty-third  Series shall not be a condition to
the


                                       11


receipt by the registered owners of the Bonds of the Twenty-third Series of such
scheduled amortization payments).

                  At the  option  of the  registered  owner,  any  Bonds  of the
Twenty-third  Series,  upon surrender  thereof for cancellation at the office or
agency of the Company in the Borough of Manhattan,  The City of New York,  shall
be  exchangeable  for a like  aggregate  principal  amount  of bonds of the same
series of other authorized denominations.

                  Bonds of the  Twenty-third  Series  shall not be  transferable
except  to any  successor  Collateral  Agent  under  the  Collateral  Agreement;
provided,   however,   that,   subject  to  compliance  with  the   registration
requirements of the Securities Act of 1933, as amended (the  "Securities  Act"),
(i) on or after the day on which the Loans are  accelerated  in accordance  with
the Credit  Agreement (the  "Acceleration  Day"), all (but not less than all) of
the Bonds of the  Twenty-third  Series shall be  transferable  by the Collateral
Agent  (together  with all (but not less than all) of the  South  Dakota  Credit
Agreement  Bonds) to or upon the order of the Lenders in full  satisfaction  and
discharge  of the  Loans  and the  Obligations  (as  defined  in the  Collateral
Agreement)  pursuant  to  Section  4.1 of the  Collateral  Agreement,  and  (ii)
following  such  transfer by the  Collateral  Agent,  Bonds of the  Twenty-third
Series shall be transferable  (without restriction (except as hereinafter in the
following two paragraphs described)) by the registered owners thereof.

                  As a condition  precedent  to any transfer of the Bonds of the
Twenty-third  Series by the Collateral  Agent, the Collateral Agent shall submit
to the Company, the Corporate Trustee and, if applicable,  any bond registrar or
transfer  agent for the Bonds of the  Twenty-third  Series (in  addition  to all
other  documents  and  instruments  required  to be  submitted  pursuant  to the
Mortgage) a certificate of the Collateral  Agent,  signed by a person purporting
to be its  duly  authorized  officer,  certifying  that the  transferee  in such
transfer is a successor  Collateral Agent under the Collateral Agreement or that
the  transferees  in such  transfer  are the  Lenders  or  persons  or  entities
specified by the Lenders to which on or after the  Acceleration Day all (but not
less  than all) of the Bonds of the  Twenty-third  Series  and all (but not less
than all) of the South Dakota Credit  Agreement  Bonds are being  transferred in
full  satisfaction and discharge of the Loans and the Obligations (as defined in
the Collateral  Agreement)  pursuant to Section 4.1 of the Collateral  Agreement
(and the Corporate  Trustee may conclusively  presume the statements in any such
certificate of the Collateral  Agent to be correct and shall be fully  protected
in relying thereon). As a condition precedent to any transfer of any Bond of the
Twenty-third Series to a transferee other than a successor Collateral Agent, the
transferor in such transfer shall deliver to the Company,  the Corporate Trustee
and, if  applicable,  any bond  registrar or transfer agent for the Bonds of the
Twenty-third Series (in addition to all other documents and instruments required
to be submitted pursuant to the Mortgage),  (i) an opinion of counsel reasonably
satisfactory to the Company, the Corporate Trustee and, if applicable,  any bond
registrar or transfer agent for the Bonds of the Twenty-third  Series, or (ii) a
certificate of the transferor in such transfer, signed by a person purporting to
be its duly authorized  officer,  reasonably  satisfactory  to the Company,  the
Corporate  Trustee and, if applicable,  the bond registrar or transfer agent for
the Bonds of the  Twenty-third  Series,  in either case, to the effect that such
transfer is either (A) covered by an  effective  registration  statement  of the
Company under the Securities Act



                                       12


(setting forth the  registration  number and the date of  effectiveness  of such
registration  statement),  or (B) exempt from registration  under the Securities
Act (setting forth the applicable  exemption from registration being relied upon
and the reason such exemption is applicable to such transfer).

                  Any transfer of Bonds of the Twenty-third  Series (i) shall be
subject  to the  provisions  of  Section  12 of the  Mortgage,  except  that the
provisions  of the last two sentences of such Section 12 shall not be applicable
to any transfer of Bonds of the Twenty-third  Series which occurs on or prior to
the Remedy Exercise Day (as hereinafter  defined) (and the Company hereby waives
the provisions of such sentences  with respect to any such  transfer),  and (ii)
shall  be  made at the  office  or  agency  of the  Company  in the  Borough  of
Manhattan, The City of New York.

                  The Company hereby waives any right to make any charge for any
exchange or transfer of Bonds of the Twenty-third Series by the Collateral Agent
or any person or entity that is a direct transferee of the Collateral Agent (but
not by any other  transferee of Bonds of the  Twenty-third  Series),  whether to
reimburse itself for any tax or taxes or other governmental  charge or otherwise
(it being understood that the Company shall pay any tax or taxes or governmental
or other  charge  which may be payable by reason of any  exchange or transfer of
Bonds of the Twenty-third Series by the Collateral Agent or any person or entity
that is a direct  transferee  of the  Collateral  Agent).  However,  the Company
reserves the right to require  payment of a sum  sufficient  to cover any tax or
taxes or governmental or other charge that may be imposed in connection with any
transfer or exchange of Bonds of the Twenty-third Series by any registered owner
other  than  the  Collateral  Agent or any  person  or  entity  that is a direct
transferee of the Collateral Agent,  other than any exchange pursuant to Section
15, 54 or 115 of the Indenture not involving any transfer.

                  The Company has appointed The Bank of New York as its agent to
receive Bonds of the  Twenty-third  Series presented or surrendered for payment,
to receive Bonds of the  Twenty-third  Series  surrendered  for  registration of
transfer or exchange  and to receive  notices and demands to or upon the Company
in respect of the Bonds of the  Twenty-third  Series and the Indenture;  and the
corporate trust office of The Bank of New York in the Borough of Manhattan,  The
City of New York shall be the office or agency of the  Company in the Borough of
Manhattan, The City of New York at which such presentations, surrenders, notices
and demands may be made or served.

                  Upon the delivery of this Twenty-third Supplemental Indenture,
Bonds  of  the  Twenty-third   Series  in  the  aggregate  principal  amount  of
$280,000,000  are to be issued  forthwith and will be Outstanding in addition to
the bonds hereinbefore stated to be Outstanding.

                  Bonds  of the  Twenty-third  Series  shall be  subject  to the
following redemption and other terms and conditions:

                  (I)  Bonds of the  Twenty-third  Series  shall be  subject  to
redemption  as  follows  (but  shall  not  otherwise  be or  become  subject  to
redemption, whether at the option of



                                       13


the holders  thereof or the Company or  pursuant  to any other  requirements  or
provisions of the Indenture):  (A) on each day on which the Loans are subject to
prepayment in accordance with the Credit  Agreement,  Bonds of the  Twenty-third
Series shall be subject to redemption in an aggregate  principal amount equal to
the Applicable Share of the aggregate  principal amount of the Loans that are so
subject to prepayment on such day; and (B) on the  Acceleration  Day, the entire
aggregate  principal  amount of the Bonds of the  Twenty-third  Series  shall be
subject to redemption (the "Acceleration Redemption"); in each case, without any
necessity  for notice or call by the Company or by the  Corporate  Trustee (such
notice  and call  being  waived  by the  registered  owners  of the Bonds of the
Twenty-third  Series by the acceptance of the Bonds of the  Twenty-third  Series
and in connection with each Redemption Demand hereinafter described). Redemption
of Bonds of the Twenty-third  Series shall be at a redemption price equal to the
principal  amount of such Bonds of the  Twenty-third  Series (without  premium),
together  with interest  accrued on said  principal to and including the date of
redemption (collectively, a "Redemption Amount"). In the event of any failure by
the Company to pay when due the Redemption Amount with respect to any redemption
of Bonds of the  Twenty-third  Series,  interest  shall  accrue  on such  unpaid
Redemption  Amount at the rates (and in amounts equal to the Applicable Share of
the amounts) of interest that accrue on the  corresponding  unpaid  principal of
and interest on the Loans in accordance with the Credit Agreement.

                  The  Corporate  Trustee  may  conclusively   presume  that  no
redemption  of Bonds of the  Twenty-third  Series is  required  pursuant to this
subdivision  (I) unless and until it shall have  received a written  notice from
the  Administrative  Agent,  signed  by a  person  purporting  to  be  its  duly
authorized  officer,  stating that the Loans are subject to  prepayment  or have
been  accelerated,  in either case, in accordance  with the Credit  Agreement (a
"Redemption Demand").  Each Redemption Demand also shall state the date on which
the Loans are subject to  prepayment  or  acceleration  in  accordance  with the
Credit  Agreement,  the principal amount of the Loans subject to such prepayment
or acceleration on such date, the principal  amount of Bonds of the Twenty-third
Series  to be  redeemed  on  such  date in  accordance  with  this  Twenty-third
Supplemental  Indenture by reason of such  prepayment or  acceleration,  and the
Redemption Amount payable with respect to such Bonds of the Twenty-third  Series
(determined in accordance  with this  Twenty-third  Supplemental  Indenture) and
setting  forth the  amounts  of the  respective  portions  thereof  representing
principal  of and  interest  on such  Bonds  of the  Twenty-third  Series.  Each
Redemption  Demand shall be  accompanied  by a written  waiver by the Collateral
Agent,  as  registered  owner  of all  Bonds  of the  Twenty-third  Series  then
Outstanding,  of notice of redemption  and call for redemption by the Company or
the  Corporate  Trustee  of the  Bonds of the  Twenty-third  Series  subject  to
redemption as described in such  Redemption  Demand.  The Corporate  Trustee may
conclusively  presume the statements  contained in each Redemption  Demand to be
correct (and the Corporate Trustee shall be fully protected in relying thereon).

                  (II)  For the  avoidance  of any  doubt  (in  the  case of the
following  clauses (i) and (ii)) and  notwithstanding  anything herein or in any
Bond of the  Twenty-third  Series to the contrary  other than the  provisions of
subdivision (IV) below (in the case of the following clause (iii)): (i) prior to
the Remedy Exercise Day (as hereinafter  defined),  each payment of



                                       14


principal  of or interest on the Bonds of the  Twenty-third  Series that becomes
due and payable on any day in  accordance  with this  Twenty-third  Supplemental
Indenture  (whether by reason of stated due date,  acceleration,  redemption  or
otherwise)  shall  correspond  to,  and be equal to the  Applicable  Share of, a
payment of principal of or interest on the Loans that becomes due and payable on
such day in accordance with the Credit Agreement;  (ii) on the Acceleration Day,
the Redemption  Amount with respect to the Acceleration  Redemption shall be due
and  payable;  and (iii) on and after the Remedy  Exercise  Day (as  hereinafter
defined), (a) the Redemption Amount with respect to the Acceleration  Redemption
shall bear  interest (to the extent  permitted by law in the case of interest on
the portion of the  Redemption  Amount  representing  interest on the applicable
Bonds) at a  variable  rate per annum  which rate for each day shall be equal to
the Prime-Based Rate (as hereinafter  defined and as calculated by the Corporate
Trustee) for such day plus 6.75%,  payable to the registered owners of the Bonds
of the  Twenty-third  Series in the  manner  provided  in the  Mortgage  for the
payment of defaulted interest (including, without limitation, and if applicable,
Section 76 of the Mortgage (as  supplemented),  and (b) payments of principal of
and interest on the Bonds of the  Twenty-third  Series shall cease to correspond
to  payments  of  principal  of and  interest  on the  Loans  (and  shall not be
satisfied and discharged by the satisfaction and discharge of the Loans).

                  As used  herein,  "Remedy  Exercise  Day" means the day (on or
after the Acceleration Day) on which all (but not less than all) of the Bonds of
the  Twenty-third  Series  and all (but not less than  all) of the South  Dakota
Credit  Agreement Bonds are  transferred by the Collateral  Agent to or upon the
order of the Lenders in full  satisfaction  and  discharge  of the Loans and the
Obligations (as defined in the Collateral  Agreement) pursuant to Section 4.1 of
the Collateral  Agreement (as such transfer is evidenced by the  registration in
the names of the  transferees  in such transfer of  certificates  evidencing all
(but not less than all) of the Bonds of the Twenty-third Series and all (but not
less  than all) of the South  Dakota  Credit  Agreement  Bonds).  The  Corporate
Trustee may  conclusively  presume that the Remedy Exercise Day has not occurred
unless and until it shall have  received a written  notice  from the  Collateral
Agent, signed by a person purporting to be its duly authorized officer,  stating
that the Remedy  Exercise Day has occurred  (the "Remedy  Exercise Day Notice").
The  Remedy  Exercise  Day  Notice  (i) shall  set forth the date of the  Remedy
Exercise  Day,  (ii) in the case of any such  transfer with respect to which the
Corporate Trustee is not the transfer agent, have attached thereto,  as evidence
of the  transfer of the Bonds of the  Twenty-third  Series and the South  Dakota
Credit  Agreement  Bonds that gave rise to the occurrence of the Remedy Exercise
Day, copies of  certificates  registered in the names of the transferees in such
transfer of all (but not less than all) of the Bonds of the Twenty-third  Series
and all (but not less than all) of the South Dakota Credit  Agreement Bonds, and
(iii) if the Remedy Exercise Day Notice is received by the Corporate  Trustee on
a day  other  than the  Remedy  Exercise  Day,  the Prime  Rate (as  hereinafter
defined)  for each day on and after the Remedy  Exercise Day and on and prior to
the Business Day on which the Corporate Trustee received the Remedy Exercise Day
Notice.  The Corporate  Trustee may  conclusively  presume the statements in the
Remedy  Exercise Day Notice to be correct (and the  Corporate  Trustee  shall be
fully protected in relying thereon).



                                       15


                  As used herein,  "Prime-Based  Rate" means,  with respect to a
particular day (on or after the Remedy  Exercise Day), the higher rate per annum
of: (i) the "Prime Rate" (as  hereinafter  defined) for such day; and (ii) 4.0%.
As used  herein,  "Prime Rate"  means,  with  respect to a  particular  day, the
"Prime-1  Rate" for such day as such rate shall  appear on the Business Day next
succeeding such day on the display on Moneyline Telerate,  Inc. or any successor
service  on page 128 or any  page  that may  replace  page 128 on such  service;
provided that (a) if such day is not a Business Day, the Prime Rate for such day
shall be such rate for the next  preceding  Business  Day as so appearing on the
next  succeeding  Business  Day, and (b) if no such rate so appears on such next
succeeding  Business  Day, the Prime Rate for such day shall be the "prime rate"
for such day (or,  if such day is not a  Business  Day,  for the next  preceding
Business  Day) as such rate appears on the next  succeeding  Business Day in the
Wall  Street  Journal  under the  caption  "Money  Rates" (or if the Wall Street
Journal ceases to be published or of general  circulation,  such other financial
journal or  newspaper  of general  circulation  as is selected by the  Corporate
Trustee);  provided  further that, if no rate so appears on such next succeeding
Business  Day in the Wall  Street  Journal  or such other  financial  journal or
newspaper of general circulation, the Prime Rate for such day shall be the Prime
Rate in  effect  with  respect  to the day on  which  the  Prime  Rate  was last
determinable in accordance with the foregoing provisions of this definition; and
provided  further  that the  Prime  Rate for each day on and  after  the  Remedy
Exercise Day and on and prior to the Business Day on which the Corporate Trustee
received  the Remedy  Exercise  Day Notice  shall be (i) the rate  stated in the
Remedy  Exercise  Day Notice as the Prime Rate for such day,  or (ii) if no such
rate for such day is stated in the Remedy  Exercise  Day Notice,  the Prime Rate
for the Business  Day next  succeeding  the Business Day on which the  Corporate
Trustee  received the Remedy  Exercise Day Notice (as  determined  in accordance
with the foregoing provisions of this definition).

                  (III) Prior to the Remedy  Exercise Day, the obligation of the
Company to make each  payment of  principal  of or  interest on the Bonds of the
Twenty-third  Series  that  becomes  due and  payable  in  accordance  with this
Twenty-third  Supplemental Indenture (i) shall be fully satisfied and discharged
if the corresponding  payment of the principal of or interest on the Loans shall
have been fully paid under and in accordance with the Credit Agreement, and (ii)
shall be partially satisfied and discharged if the corresponding  payment of the
principal of or interest on the Loans shall have been  partially  paid under and
in accordance with the Credit Agreement (such partial satisfaction and discharge
with respect to the Bonds of the Twenty-third Series to be in an amount equal to
the Applicable  Share of the amount of such partial  payment with respect to the
Loans). Prior to the Remedy Exercise Day, the Corporate Trustee may conclusively
presume that the  obligation of the Company to make payments with respect to the
principal  of and  interest on the Bonds of the  Twenty-third  Series shall have
been fully satisfied and discharged unless and until the Corporate Trustee shall
have received a written notice from the Administrative Agent, signed by a person
purporting to be its duly authorized  officer,  stating (i) that the Company has
failed to make timely  payment in full or in part of an amount of  principal  of
and/or interest on the Loans which became due and payable in accordance with the
Credit  Agreement,  (ii) the amount and date of such  payment  of  principal  of
and/or  interest on the Loans which the Company has failed to make in accordance
with the Credit Agreement, and (iii) the amount of principal of


                                       16


and/or  interest on the Bonds of the  Twenty-third  Series which,  in accordance
with  this  Twenty-third  Supplemental  Indenture,  has not been  satisfied  and
discharged by reason of such failure of the Company.  The Corporate  Trustee may
conclusively  presume  the  statements  contained  in any such  notice  from the
Administrative  Agent to be correct unless and until the Corporate Trustee shall
receive a  subsequent  and/or  modified  notice  from the  Administrative  Agent
pursuant  to and in  accordance  with this  subdivision  III (and the  Corporate
Trustee shall be fully protected in relying thereon).  Without limitation of the
foregoing,  and for the  avoidance of any doubt,  it is  expressly  stated that,
prior to the Remedy Exercise Day, the Corporate Trustee shall not be responsible
for (i) the calculation of interest on the Bonds of the Twenty-third  Series, or
(ii)  the  determination  of any  amount  (including,  without  limitation,  any
principal  of or interest on the Loans) that is payable or paid under the Credit
Agreement.

                  (IV) Nothing herein or in any of the Bonds of the Twenty-third
Series (including,  without  limitation,  any reference to the principal payable
with respect to the Bonds of the  Twenty-third  Series being  determined  on the
basis of the  Applicable  Share of the  principal  payable  with  respect to the
Loans)  shall,  or shall be deemed or construed  to, (i) increase the  aggregate
principal  amount of the Bonds of the  Twenty-third  Series that are Outstanding
from time to time,  (ii) cause or permit an amount of  principal of the Bonds of
the Twenty-third  Series to be or to become due and payable which, when added to
all other principal of such Bonds theretofore  paid,  exceeds  $280,000,000,  or
(iii) cause or permit to be or to become due and  payable  interest on the Bonds
of the Twenty-third Series which is payable on any principal of the Bonds of the
Twenty-third  Series  that is in  excess  of the  principal  of the Bonds of the
Twenty-third  Series as  restricted  pursuant to the  preceding  clauses (i) and
(ii).

                                   ARTICLE II

                   Additional Covenant for the Benefit of the
                        Bonds of the Twenty-third Series

                  Section 2.1 The Company  covenants  that so long as any of the
Bonds of the Twenty-third Series shall remain Outstanding, (i) the Company shall
not  submit  a  request  to the  Corporate  Trustee  or  otherwise  apply to the
Corporate Trustee for (a) the  authentication  and delivery of bonds pursuant to
Article V, VI or VII of the Mortgage (as  supplemented),  (b) the application of
insurance proceeds pursuant to Section 37 of the Mortgage (as supplemented), (c)
the release of property  (including  the withdrawal of cash) pursuant to Article
XI of the Mortgage (as  supplemented),  or (d) the  execution and delivery of an
indenture  supplemental to such Mortgage (as supplemented)  (any such request or
application  being  referred to as an  "Application"),  in any case,  unless the
Company  shall have given to the  Administrative  Agent,  at least the  Required
Number of Days (as hereinafter defined) prior to the submission to the Corporate
Trustee of such  Application,  notice of its intention to apply to the Corporate
Trustee for the taking of such action (an  "Administrative  Agent Notice"),  and
(ii) the Company shall have furnished to the Corporate  Trustee,  in addition to
the other materials required by the provisions of the Mortgage (as supplemented)
to be furnished to the Corporate Trustee as part of such Application,  a copy of
the Administrative


                                       17


Agent Notice with respect to such Application and a certificate of the President
or a Vice  President  of the  Company to the effect  that at least the  Required
Number  of Days has  elapsed  subsequent  to the  giving by the  Company  to the
Administrative  Agent of the  Administrative  Agent  Notice with respect to such
Application  and  prior  to the  submission  to the  Corporate  Trustee  of such
Application  (an  "Administrative  Agent  Notice  Certificate").  Receipt by the
Corporate  Trustee  of a  copy  of  the  Administrative  Agent  Notice  and  the
Administrative  Agent Notice Certificate with respect to an Application shall be
conditions  to the taking of any action  applied  for in such  Application.  The
Corporate  Trustee shall have no duty to inquire into, may conclusively  presume
the  correctness  of,  and  shall  be  fully  protected  in  relying  upon,  any
Administrative Agent Notice and any Administrative Agent Notice Certificate.  As
used herein,  "Required  Number of Days" means,  with respect to an Application,
three  (3)  Business  Days  (as  defined  in  Article  I,  Section  1.1 of  this
Twenty-third Supplemental Indenture) or such shorter period of time to which the
Administrative  Agent shall have agreed in writing.  For the avoidance of doubt,
it is expressly stated that (i) an Administrative  Agent Notice may cover one or
more  different  Applications  and one or more  different  actions  to be  taken
pursuant to the same or different  provisions of the Mortgage (as supplemented),
and (ii)  notwithstanding  the number of  Applications  or actions covered by an
Administrative  Agent Notice, such Administrative  Agent Notice need be given by
the Company to the Administrative  Agent only once (at least the Required Number
of  Days  prior  to  the  submission  to the  Corporate  Trustee  of  the  first
Application covered by such Administrative Agent Notice).

                                  ARTICLE III

                             Amendments to Mortgage

                  Section 3.1 . So long as any of the Bonds of the  Twenty-third
Series remain Outstanding, Section 7 of the Mortgage is amended by adding at the
end thereof the following additional paragraphs:

                  If any bonds Outstanding at the date of a Net Earning
         Certificate  (except any for the  refunding of which the bonds
         applied for are to be issued) or any bonds then applied for in
         pending applications  (including the application in connection
         with which such Net Earning  Certificate  is made) bear or are
         to bear  interest at a variable  rate or  variable  rates such
         that the interest  requirements with respect to such bonds for
         any twelve (12) month period prior to the stated maturity date
         of such  bonds  are not  determinable  at the date of such Net
         Earning  Certificate  (any such  bonds  being  referred  to as
         "Variable  Rate  Bonds"),  then (in lieu of setting  forth the
         Annual Interest  Requirements (as otherwise prescribed by this
         Section 7), such Net Earning  Certificate  shall (A) set forth
         (i) the sum of the  amounts  required  by clauses  (i) through
         (iv) of  paragraph  (B) of this Section 7 (in the case of such
         clauses (i) and (ii),  excluding the interest  requirements in
         respect of the  Variable  Rate Bonds) (the sum of such amounts
         being  referred  to herein and to be  referred  to in such Net
         Earning Certificate as the "Fixed Rate Interest Amount"),  and
         (ii) the amount  (referred  to herein and to be referred to in
         such


                                  18


         Net Earning  Certificate  as the "Maximum  Permitted  Variable
         Rate  Interest  Amount") by which (x) one-half of the Adjusted
         Net  Earnings  of the  Company  set forth in such Net  Earning
         Certificate,  exceeds (y) the Fixed Rate  Interest  Amount set
         forth in such Net  Earning  Certificate,  and (ii) if such Net
         Earning  Certificate  is  accompanied  by a certificate  of an
         independent (as hereinafter  defined) investment banking firm,
         signed by a  managing  director  or  officer  thereof,  to the
         effect that, based upon historical fluctuations in the indices
         upon which the  variable  rate or variable  rates borne by the
         Variable  Rate Bonds are based,  and taking  into  account the
         margins to be added to or subtracted  from such indices and/or
         any other  adjustments to be made in determining such variable
         rate or variable rates and prevailing and projected conditions
         in the markets influencing such indices,  such independent (as
         hereinafter  defined)  investment banking firm believes (or is
         of the  view),  as of the date of such  certificate,  that the
         aggregate  amount  of  interest  to be  payable  on all of the
         Variable  Rate Bonds  during any period of twelve  (12) months
         prior to the stated  maturity date last to occur of any of the
         Variable  Rate Bonds will not  exceed  the  Maximum  Permitted
         Variable Rate Interest Amount (as calculated by the Company in
         such Net Earning Certificate without any responsibility on the
         part of such independent (as hereinafter  defined)  investment
         banking firm for the  calculation  thereof),  such Net Earning
         Certificate  shall be deemed for all  purposes of the Mortgage
         (including, without limitation,  Sections 26, 28 and 29 of the
         Mortgage)  to show  Adjusted Net Earnings of the Company to be
         as  required  by Section 27 of the  Mortgage.  As used in this
         Section 7, "independent"  means, with respect to an investment
         banking  firm that  provides a  certificate  pursuant  to this
         Section 7, that: (i) such investment banking firm is competent
         to provide such certificate (and such investment  banking firm
         shall be conclusively presumed to be competent to provide such
         certificate if such  investment  banking firm is an investment
         banking firm of nationally  recognized standing and engages in
         interest rate swap  transactions in the ordinary course of its
         business); (ii) such investment banking firm does not have any
         direct or indirect  investment  in the Company or in any bonds
         that, as of the date of such  certificate,  are Outstanding or
         the subject of a pending  application for  authentication  and
         delivery under the Mortgage  (including,  without  limitation,
         any bonds that are subject of the Net Earning  Certificate  to
         which such  certificate  relates) or in any  affiliate  of the
         Company (other than de minimus  amounts of loans or securities
         of the Company or affiliates of the Company held in its or its
         affiliates'  accounts and any  investment in, or ownership of,
         additional securities or loans of the Company or affiliates of
         the Company resulting from its market making activities in the
         ordinary  course  of  its  business);  (iii)  such  investment
         banking firm is not, and none of its officers or directors is,
         an affiliate of the Company;  and (iv) such investment banking
         firm is not acting as an underwriter with respect to any bonds
         that are the subject of the Net Earning  Certificate  to which
         such certificate  relates or as an arranger or


                                  19


         provider  of  the  loans,   extensions   of  credit  or  other
         securities  (if any)  for  which  such  bonds  are  collateral
         security.

                  If the Company is a successor corporation (within the
         meaning of Section 86 of this  Indenture),  the  "Adjusted Net
         Earnings  of the  Company"  as set  forth in each Net  Earning
         Certificate  shall be  calculated as described in the last two
         sentences of Section 86 of this Indenture.

                  Section  3.2 So long as any of the  Bonds of the  Twenty-third
Series  remain  Outstanding,  Section 27 of the Mortgage is amended by adding at
the end thereof the following additional sentence:

         As described in the penultimate paragraph of Section 7 hereof,
         and subject to the conditions therein specified, a Net Earning
         Certificate  shall be deemed to show  Adjusted Net Earnings of
         the Company to be as required by this  Section 27 (without any
         necessity for such Net Earning  Certificate  to specify Annual
         Interest Requirements).

                  Section  3.3 So long as any of the  Bonds of the  Twenty-third
Series are  Outstanding,  Section 86 of the Mortgage is amended by adding at the
end thereof the following additional sentences:

         For the avoidance of any doubt, it is expressly stated that in
         the event that a successor  corporation  (having  succeeded to
         and having been substituted for the Company in accordance with
         this Section 86) shall exercise any right under this Indenture
         (whether as to the issuance of  additional  bonds  (including,
         without limitation, the Bonds of the Twenty-third Series), the
         withdrawal  of cash,  the release of  property,  the taking of
         credit under  Section 39 or Section 40 hereof,  or  otherwise)
         and a Net Earning  Certificate  shall be required by the terms
         of this Indenture in connection  therewith,  the "Adjusted Net
         Earnings of the Company" shall be, and shall be stated in such
         Net  Earning  Certificate  to be, the lesser of (A) the amount
         (for  the  applicable   period  selected  in  accordance  with
         paragraph  (A) of Section 7 of this  Indenture)  determined in
         accordance  with  paragraph (A) of Section 7 of this Indenture
         (and the other  provisions of such Section 7 that are relevant
         to such  paragraph) on the basis of (i) the items set forth in
         clauses (1), (2), (4) and (6) of paragraph (A) of such Section
         7  being  such  portions  of  such  items  of  such  successor
         corporation  as are  reasonably  allocated  by such  successor
         corporation to or from the Mortgaged and Pledged Property as a
         plant or plants and an operating  system or operating  systems
         (and  if,  on the  date  of a Net  Earning  Certificate,  such
         successor corporation shall be a party to any other general or
         first  mortgage  indenture  and  deed  of  trust  relating  to
         property other than the Mortgaged and Pledged Property and the
         lien of such other mortgage  indenture and deed of trust shall
         not have been discharged,  such reasonable allocation shall be
         in a manner consistent with the manner of allocation  utilized
         and/or to be utilized by such successor  corporation in


                                  20


         making  calculations  of the  "Adjusted  Net  Earnings  of the
         Company"  (or other  comparable  term) under and as defined in
         such other  mortgage  indenture  and deed of trust),  (ii) the
         item set forth in clause (8) of paragraph  (A) of such Section
         7 being calculated without regard to income (net) derived from
         any  electric  and/or gas utility  business  of the  successor
         corporation in which the Mortgaged and Pledged Property is not
         utilized (but  otherwise in  accordance  with such Section 7),
         and (iii) the item set forth in clause (10) of  paragraph  (A)
         of  such  Section  7  being   calculated   without  regard  to
         sub-clause  (b) of  such  clause  and  without  regard  to the
         proviso to such clause (but otherwise in accordance  with such
         clause),  and  (B)  the  amount  (for  the  applicable  period
         selected in accordance with paragraph (A) of Section 7 of this
         Indenture)  determined  in  accordance  with  paragraph (A) of
         Section 7 of this Indenture (and the other  provisions of such
         Section 7 that are  relevant to such  paragraph)  (without any
         allocation or  distinction  as to the  derivation of the items
         set  forth  in any of the  clauses  of  paragraph  (A) of such
         Section 7, other than  allocation or  distinction  between (i)
         the  electric  and/or gas utility  business or  businesses  in
         which such successor  corporation  is engaged  (whether or not
         the Mortgaged  and Pledged  Property is utilized in connection
         therewith), and (ii) the other business or businesses in which
         such  successor   corporation  is  engaged  (with  such  other
         business or businesses  being given effect under the items set
         forth in clauses (8) and (10) of paragraph (A) of such Section
         7)).  Each  such  Net  Earning  Certificate  shall  contain  a
         statement of the signers of such Net Earning Certificate that,
         in the opinion of such signers,  the  allocations  made in the
         calculations  of "Adjusted Net Earnings of the Company" as set
         forth in such Net Earning  Certificate  are in accordance with
         the requirements of the preceding sentence of this Section 86.

                                   ARTICLE IV

                                  Miscellaneous

                  Section 4.1 Except as otherwise expressly provided herein, the
terms  defined in the  Mortgage,  as  heretofore  supplemented,  shall,  for all
purposes of this Twenty-third Supplemental Indenture, have the meaning specified
in the Mortgage, as heretofore supplemented.

                  Section  4.2 The  Trustees  hereby  accept  the  trust  herein
declared,  provided,  created or supplemented and agree to perform the same upon
the terms and conditions herein and in the Mortgage, as heretofore supplemented,
set forth and upon the following terms and conditions.

         The Trustees shall not be responsible in any manner whatsoever
         for or in  respect  of the  validity  or  sufficiency  of this
         Twenty-third  Supplemental  Indenture  or for or in respect of
         the recitals  contained herein, all of which recitals are made
         by the Company  solely.  In  general,  each and every term and
         condition  contained  in  Article  XVII  of the  Mortgage,  as
         heretofore


                                  21


         supplemented,   shall   apply  to  and   form   part  of  this
         Twenty-third  Supplemental  Indenture  with the same force and
         effect as if the same were  herein set forth in full with such
         omissions,  variations  and  insertions,  if  any,  as  may be
         appropriate to make the same conform to the provisions of this
         Twenty-third Supplemental Indenture.

                  Section  4.3  Whenever  in  this   Twenty-third   Supplemental
Indenture any of the parties hereto is named or referred to, this shall, subject
to the  provisions  of  Articles  XVI and XVII of the  Mortgage,  as  heretofore
supplemented, be deemed to include the successors and assigns of such party, and
all the covenants and  agreements in this  Twenty-third  Supplemental  Indenture
contained  by or on behalf of the  Company,  or by or on behalf of the  Trustees
shall,  subject as aforesaid,  bind and inure to the respective  benefits of the
respective successors and assigns of such parties, whether so expressed or not.

                  Section   4.4  Nothing  in  this   Twenty-third   Supplemental
Indenture,  expressed or implied, is intended, or shall be construed,  to confer
upon,  or to give to, any person,  firm or  corporation,  other than the parties
hereto and the holders of the bonds and coupons Outstanding under the Indenture,
any right, remedy or claim under or by reason of this Twenty-third  Supplemental
Indenture or any covenant, condition,  stipulation, promise or agreement hereof,
and all the covenants, conditions, stipulations, promises and agreements in this
Twenty-third  Supplemental  Indenture  contained  by or on behalf of the Company
shall be for the sole and exclusive  benefit of the parties  hereto,  and of the
holders of the bonds and coupons now, or to be, Outstanding under the Indenture.

                  Section 4.5 This Twenty-third  Supplemental Indenture shall be
executed in several counterparts,  each of which shall be an original and all of
which shall constitute but one and the same instrument.


                            [Signature Pages Follow]


                                  22


                  IN WITNESS  WHEREOF,  NORTHWESTERN  CORPORATION has caused its
name to be hereunto affixed,  and this instrument to be signed and sealed by its
President  or one of its Vice  Presidents,  and its seal to be  attested  by its
Secretary or one of its  Assistant  Secretaries  for and in its behalf,  and THE
BANK OF NEW YORK, in token of its  acceptance of the trust hereby  created,  has
caused its  corporate  name to be hereunto  affixed,  and this  instrument to be
signed and sealed by one of its Vice  Presidents  or one of its  Assistant  Vice
Presidents,  and its corporate  seal to be attested by one of its Assistant Vice
Presidents, Assistant Secretaries or Assistant Treasurers, and MARYBETH LEWICKI,
for all like purposes, has hereunto set her hand and affixed her seal, as of the
day and year first above written.



                             NORTHWESTERN CORPORATION



                             By:    /s/ Eric R. Jacobsen
                                    ---------------------------------
                             Name:  Eric R. Jacobsen
                             Title: Senior Vice President, General Counsel,
                                    Chief Legal Officer and Assistant
                                    Corporate Secretary


[SEAL]

Attest:

 /s/ Alan D. Dietrich
- -----------------------------
Name:     Alan D. Dietrich
Title:    Corporate Secretary



Executed, sealed and delivered by
NORTHWESTERN CORPORATION
in the presence of:


 /s/ Karen L. Smook
- -----------------------------

 /s/ Corinne Bohrer
- -----------------------------







         STATE OF SOUTH DAKOTA)
                              : ss.
         COUNTY OF MINNEHAHA  )

                  This instrument was acknowledged before me on this 10th day of
         February,  2003, by Eric R. Jacobsen,  Senior Vice  President,  General
         Counsel,  Chief Legal Officer and  Assistant  Corporate  Secretary,  of
         NORTHWESTERN CORPORATION, a Delaware corporation.


                                     /s/ Karen L. Smook
                                    --------------------------------------------
                                    Print Name: Karen L. Smook
                                    Notary Public for the State of South Dakota
                                    Residing at Brandon, South Dakota
                                    My Commission expires 7-12-2005

         [SEAL]





                                               THE BANK OF NEW YORK,
                                                 as Corporate Trustee


                                               By:  /s/ Barbara A. Bevelaqua
                                                    ----------------------------
                                                    Name:  Barbara A. Bevelaqua
                                                    Title: Vice President

[SEAL]


Attest:


 /s/ Stacey B. Poindexter
- ------------------------------------
Name:    Stacey B. Poindexter
Title:   Assistant Treasurer




                                                /s/ MaryBeth Lewicki
                                               ---------------------------------
                                               MARYBETH LEWICKI, as Co-Trustee


Executed,  sealed and delivered by
THE BANK OF NEW YORK and
MARYBETH  LEWICKI in the presence of:



 /s/ Jeremy Finkelstein
- -----------------------------

 /s/ Regina F. Johnson
- -----------------------------






         STATE OF NEW YORK    )
                              : ss.
         COUNTY OF NEW YORK   )

                  This instrument was acknowledged before me on this 10th day of
         February, 2003, by Barbara A. Bevelaqua,  Vice President of THE BANK OF
         NEW YORK, a New York corporation.


                                           /s/ William J. Cassells
                                          ------------------------
                                             WILLIAM J. CASSELLS
                                      Notary Public, State of New York
                                               No. 01CA5027729
                                          Qualified in Bronx County
                                       Commission Expires May 16, 2006


         [SEAL]






         STATE OF NEW YORK    )
                              : ss.
         COUNTY OF NEW YORK   )

                  This instrument was acknowledged before me on this 10th day of
February, 2003, by MARYBETH LEWICKI.


                                           /s/ William J. Cassells
                                          ------------------------
                                             WILLIAM J. CASSELLS
                                      Notary Public, State of New York
                                               No. 01CA5027729
                                          Qualified in Bronx County
                                       Commission Expires May 16, 2006



         [SEAL]





                                 Exhibit A-1 to
                       Twenty-third Supplemental Indenture


                    [FORM OF NOTICE OF REMOVAL OF CO-TRUSTEE]


                  NOTICE  IS  HEREBY  GIVEN  that the  undersigned  NORTHWESTERN
CORPORATION  has removed DOUGLAS J. MACINNES as successor  Co-Trustee  under the
Mortgage  and Deed of  Trust,  dated as of  October  1,  1945,  as  amended,  of
NorthWestern  Corporation  (as  successor  thereunder  to  NorthWestern  Energy,
L.L.C.,  in turn successor  thereunder to The Montana Power Company) to The Bank
of New York (as successor  thereunder to Guaranty Trust Company of New York) and
Douglas J. MacInnes (as indirect  successor  thereunder to Arthur E. Burke),  as
Trustees,  such removal having taken effect at the close of business on February
7, 2003.


Dated: February     , 2003

                                               NORTHWESTERN CORPORATION





                                     A-1-1




                                 Exhibit A-2 to
                       Twenty-third Supplemental Indenture


             [FORM OF NOTICE OF APPOINTMENT OF SUCCESSOR CO-TRUSTEE]


                  NOTICE  IS  HEREBY  GIVEN  that the  undersigned  NORTHWESTERN
CORPORATION,  having removed Douglas J. MACInnes as successor  Co-Trustee  under
the  Mortgage  and Deed of Trust,  dated as of October 1, 1945,  as amended,  of
NorthWestern  Corporation  (as  successor  thereunder  to  NorthWestern  Energy,
L.L.C.,  in turn successor  thereunder to The Montana Power Company) to The Bank
of New York  (successor  thereunder  to Guaranty  Trust Company of New York) and
Douglas J. MacInnes (as indirect  successor  thereunder to Arthur E. Burke),  as
Trustees,  has appointed  MARYBETH  LEWICKI as successor  Co-Trustee  under such
Mortgage and Deed of Trust, and MaryBeth Lewicki has accepted such  appointment,
effective as of the close of business on February 7, 2003.


Dated:   February     , 2003

                                               NORTHWESTERN CORPORATION




                                     A-2-1




                                  Exhibit B to
                       Twenty-third Supplemental Indenture



                                  Form of Bond








          [FORM OF FIRST MORTGAGE BOND, CREDIT AGREEMENT (2002) SERIES,
                                    DUE 2006]

      TRANSFER OF THIS BOND IS SUBJECT TO CERTAIN RESTRICTIONS ON TRANSFER
             CONTAINED IN THE MORTGAGE TO WHICH REFERENCE IS MADE IN
            THIS BOND. THE TRANSFER RESTRICTIONS ARE DESCRIBED ON THE
                              REVERSE OF THIS BOND.

                            NORTHWESTERN CORPORATION

                              First Mortgage Bond,
                    Credit Agreement (2002) Series, due 2006

No. R-                                                        $ ________________

                  NORTHWESTERN CORPORATION, a corporation organized and existing
under the laws of the State of Delaware  (the  "Company"),  for value  received,
hereby promises to pay to CREDIT SUISSE FIRST BOSTON,  AS COLLATERAL AGENT UNDER
THE BOND  COLLATERAL  AGREEMENT  to which  reference  is  hereinafter  made,  or
(subject to the transfer restrictions hereinafter described) registered assigns,
at the office or agency of the Company in the Borough of Manhattan,  The City of
New York,  the sum of  _________  dollars,  in  installments  prior to,  and the
balance on, December 1, 2006 (the "Maturity Date"), in each case, in such amount
as is hereinafter described for such installment or such balance, as applicable,
and in such coin or currency  of the United  States of America as at the time of
payment  is  legal  tender  for  public  and  private  debts,  and to pay to the
registered  owner  interest  thereon as  hereinafter  described  in like coin or
currency and at such office or agency.

                  The bonds of the  series  of which  this bond is one have been
issued to Credit Suisse First Boston,  acting through its Cayman Islands Branch,
as  collateral  agent  (together  with  its  successors  in such  capacity,  the
"Collateral  Agent") under the Bond Collateral  Agreement,  dated as of February
10, 2003 (as amended or otherwise  modified,  or as waived,  or as replaced,  in
each  case,  from time to time in  accordance  with its terms,  the  "Collateral
Agreement"),  between  the  Company  and the  Collateral  Agent,  to secure  the
obligations of the Company to pay when due the Applicable  Share (as hereinafter
defined) of the  principal of and interest on the loans (the  "Loans")  made and
outstanding  under the  Credit  Agreement,  dated as of  December  17,  2002 (as
amended or otherwise modified,  or as waived, or as replaced, in each case, from
time to time in accordance with its terms,  the "Credit  Agreement"),  among the
Company, as borrower, the several lenders from time to time parties thereto (the
"Lenders")  and Credit Suisse First Boston,  acting  through its Cayman  Islands
Branch, as administrative  agent (together with its successors in such capacity,
the "Administrative Agent").


                                      B-1



                  The  provisions  of this  bond are  continued  on the  reverse
hereof and such continued provisions shall for all purposes have the same effect
as though set fully forth at this place.

                  This instrument shall not become  obligatory until The Bank of
New York (successor to Morgan Guaranty Trust Company of New York), the Corporate
Trustee  under  the  Mortgage  (referred  to on  the  reverse  hereof),  or  its
successors thereunder,  shall have signed the form of authentication certificate
endorsed hereon.

                  IN WITNESS WHEREOF,  NORTHWESTERN  CORPORATION has caused this
instrument  to be signed in its  corporate  name by its Chairman of the Board or
its  President  or one of  its  Vice  Presidents  by his or her  signature  or a
facsimile  thereof,  and its corporate seal to be impressed or imprinted  hereon
and attested by its Secretary or one of its Assistant  Secretaries by his or her
signature or a facsimile thereof.

Dated:

                            NORTHWESTERN CORPORATION

                            By:
                               ----------------------------------------------
                                     [Title]
Attest:

- -------------------------
       [Title]

(Seal)

                              CORPORATE TRUSTEE'S
                           AUTHENTICATION CERTIFICATE

                  This  bond  is  one  of  the  bonds,   of  the  series  herein
designated, described or provided for in the within-mentioned Mortgage.

                            THE BANK OF NEW YORK,
                              as Corporate Trustee

                            By:
                               ----------------------------------------------
                                  Authorized Signatory


                                      B-2



                            [FORM OF REVERSE OF BOND]

General
- -------

                  This bond is one of an issue of bonds of the Company  issuable
in series  and is one of a series  known as its  First  Mortgage  Bonds,  Credit
Agreement (2002) Series, due 2006 (sometimes herein referred to as the "Bonds of
the Twenty-third Series"), all bonds of all series issued and to be issued under
and equally secured (except in so far as any sinking or other fund,  established
in accordance  with the provisions of the Mortgage  hereinafter  mentioned,  may
afford additional security for the bonds of any particular series) by a Mortgage
and Deed of Trust  (herein,  together with any indenture  supplemental  thereto,
including the Twenty-third  Supplemental  Indenture dated as of February 1, 2003
(the "Twenty-third Supplemental Indenture"), called the "Mortgage"), dated as of
October  1,  1945,   executed  by  The  Montana  Power   Company   (NorthWestern
Corporation,  successor  thereunder)  to Guaranty Trust Company of New York (The
Bank of New York,  successor  thereunder) and Arthur E. Burke (MaryBeth Lewicki,
successor  thereunder),  as  Trustees.  Reference  is made to the Mortgage for a
description of the property mortgaged and pledged,  the nature and extent of the
security,  the rights of the holders of the bonds and of the Trustees in respect
thereof,  the duties and  immunities of the Trustees,  the terms and  conditions
upon which the bonds are and are to be secured,  the  circumstances  under which
additional  bonds may be issued and the definition of any capitalized  term used
herein but not defined herein. With the consent of the Company and to the extent
permitted by and as provided in the Mortgage,  the rights and obligations of the
Company  and/or the rights of the holders of the bonds and/or coupons and/or the
terms and  provisions of the Mortgage may be modified or altered by  affirmative
vote of the holders of at least  66-2/3% in  principal  amount of the bonds then
Outstanding under the Mortgage and, if the rights of the holders of one or more,
but less than all,  series of bonds then  Outstanding  are to be affected,  then
also by affirmative  vote of the holders of at least 66-2/3% in principal amount
of the  bonds  then  Outstanding  of each  series  of  bonds  so to be  affected
(excluding in any case bonds disqualified from voting by reason of the Company's
interest  therein as  provided  in the  Mortgage);  provided  that,  without the
consent of the holder hereof, no such  modification or alteration  shall,  among
other things, impair or affect the right of the holder to receive payment of the
principal of and  interest on this bond,  on or after the  respective  due dates
expressed  herein, or permit the creation of any lien equal or prior to the lien
of the Mortgage or deprive the holder of the benefit of a lien on the  mortgaged
and pledged property.

                  The  principal  hereof may be declared or may become due prior
to the maturity date hereinbefore named on the conditions,  in the manner and at
the time set forth in the Mortgage,  upon the  occurrence of a default as in the
Mortgage provided.

                  No recourse  shall be had for the payment of the  principal of
or interest on this bond against any incorporator or any past, present or future
subscriber to the capital stock, stockholder, officer or director of the Company
or of any  predecessor or successor  corporation,  as such,  either  directly or
through the Company or any predecessor or successor


                                      B-3



corporation,  under  any  rule  of  law,  statute  or  constitution  or  by  the
enforcement of any assessment or otherwise, all such liability of incorporators,
subscribers,  stockholders,  officers and directors being released by the holder
or owner hereof by the  acceptance  of this bond and being  likewise  waived and
released by the terms of the Mortgage.

Transfer Provisions and Restrictions
- ------------------------------------

                  Bonds of the  Twenty-third  Series  shall not be  transferable
except  to any  successor  Collateral  Agent  under  the  Collateral  Agreement;
provided,   however,   that,   subject  to  compliance  with  the   registration
requirements of the Securities Act of 1933, as amended (the  "Securities  Act"),
(i) on or after the day on which the Loans are  accelerated  in accordance  with
the Credit  Agreement (the  "Acceleration  Day"), all (but not less than all) of
the Bonds of the  Twenty-third  Series shall be  transferable  by the Collateral
Agent  (together  with all (but not less than all) of the  South  Dakota  Credit
Agreement Bonds (as hereinafter defined)) to or upon the order of the Lenders in
full  satisfaction and discharge of the Loans and the Obligations (as defined in
the Collateral  Agreement) pursuant to Section 4.1 of the Collateral  Agreement,
and  (ii)  following  such  transfer  by  the  Collateral  Agent,  Bonds  of the
Twenty-third  Series  shall be  transferable  (without  restriction  (except  as
hereinafter in the following two paragraphs described)) by the registered owners
thereof.

                  As a condition  precedent  to any transfer of the Bonds of the
Twenty-third  Series by the Collateral  Agent, the Collateral Agent shall submit
to the Company, the Corporate Trustee and, if applicable,  any bond registrar or
transfer  agent for the Bonds of the  Twenty-third  Series (in  addition  to all
other  documents  and  instruments  required  to be  submitted  pursuant  to the
Mortgage) a certificate of the Collateral  Agent,  signed by a person purporting
to be its  duly  authorized  officer,  certifying  that the  transferee  in such
transfer is a successor  Collateral Agent under the Collateral Agreement or that
the  transferees  in such  transfer  are the  Lenders  or  persons  or  entities
specified by the Lenders to which on or after the  Acceleration Day all (but not
less  than all) of the Bonds of the  Twenty-third  Series  and all (but not less
than all) of the South Dakota Credit  Agreement Bonds (as  hereinafter  defined)
are being  transferred in full  satisfaction  and discharge of the Loans and the
Obligations (as defined in the Collateral  Agreement) pursuant to Section 4.1 of
the Collateral Agreement (and the Corporate Trustee may conclusively presume the
statements in any such  certificate  of the  Collateral  Agent to be correct and
shall be fully protected in relying  thereon).  As a condition  precedent to any
transfer of any Bond of the  Twenty-third  Series to a  transferee  other than a
successor Collateral Agent, the transferor in such transfer shall deliver to the
Company,  the  Corporate  Trustee  and, if  applicable,  any bond  registrar  or
transfer  agent for the Bonds of the  Twenty-third  Series (in  addition  to all
other  documents  and  instruments  required  to be  submitted  pursuant  to the
Mortgage), (i) an opinion of counsel reasonably satisfactory to the Company, the
Corporate  Trustee and, if applicable,  any bond registrar or transfer agent for
the Bonds of the Twenty-third Series, or (ii) a certificate of the transferor in
such transfer,  signed by a person purporting to be its duly authorized officer,
reasonably   satisfactory  to  the  Company,   the  Corporate  Trustee  and,  if
applicable,  the  bond  registrar  or  transfer  agent  for  the  Bonds  of  the
Twenty-third  Series, in either case, to the


                                      B-4



effect that such  transfer is either (A)  covered by an  effective  registration
statement  of  the  Company  under  the   Securities   Act  (setting  forth  the
registration   number  and  the  date  of  effectiveness  of  such  registration
statement),  or (B) exempt from  registration  under the Securities Act (setting
forth the  applicable  exemption  from  registration  being  relied upon and the
reason such exemption is applicable to such transfer).

                  Any such  transfer is to be made as prescribed in the Mortgage
by the registered owner hereof in person, or by his duly authorized attorney, at
the office or agency of the Company in the Borough of Manhattan, The City of New
York, upon surrender and cancellation of the applicable Bond of the Twenty-third
Series, and, thereupon,  a new fully registered  temporary or definitive bond of
the same series for a like principal  amount will be issued to the transferee in
exchange therefor as provided in the Mortgage.  The Company and the Trustees may
deem and treat the person in whose name any Bond of the  Twenty-third  Series is
registered as the absolute  owner  thereof for the purpose of receiving  payment
and for all other  purposes  and neither the Company nor the  Trustees  shall be
affected by any notice to the contrary.

                  In  the  manner  prescribed  in  the  Mortgage,  Bonds  of the
Twenty-third Series upon surrender thereof,  for cancellation,  at the office or
agency of the Company in the  Borough of  Manhattan,  The City of New York,  are
exchangeable  for a like aggregate  principal  amount of registered bonds of the
same series of other authorized denominations.

                  As provided in the Mortgage, the Company shall not be required
to make  transfers  or exchanges of bonds of any series for a period of ten days
next  preceding  any interest  payment  date for bonds of said  series,  or next
preceding  any  designation  of bonds of said series to be  redeemed;  provided,
however,  that  pursuant  to  a  waiver  by  the  Company  in  the  Twenty-Third
Supplemental  Indenture,  these  restrictions  shall  not be  applicable  to any
transfer  of the  Bonds of the  Twenty-third  Series  on or prior to the  Remedy
Exercise Day (as hereinafter defined).

Principal
- ---------

         Principal of the Bonds of the Twenty-third  Series,  of which this bond
is one, is  scheduled  to be paid as follows:  (A) on the last  Business Day (as
hereinafter defined) of each March, June, September and December occurring prior
to the Maturity Date (commencing March 31, 2003), an installment of principal of
the Bonds of the Twenty-third Series in an amount equal to $700,000 (said amount
representing  one  quarter  of one  percent  (0.25%) of the  original  aggregate
principal  amount of the Bonds of the  Twenty-third  Series) is due and payable;
and (B) on the Maturity  Date,  the balance of the principal of the Bonds of the
Twenty-third  Series  is  due  and  payable;  in  each  case,  unless  an  equal
installment  or balance of the  principal of the Loans is not due and payable on
such Business Day or the Maturity  Date, as applicable,  in accordance  with the
Credit  Agreement  by reason of prior  prepayment  of the Loans (in which event,
there shall be due and payable on the Bonds of the  Twenty-third  Series on such
Business Day or on the Maturity Date, as  applicable,  an amount of principal of
said Bonds equal to the Applicable Share of the amount of principal of the


                                      B-5



Loans  that  is  payable  on  such  Business  Day or on the  Maturity  Date,  as
applicable,  in accordance with the Credit Agreement). As used herein, "Business
Day" means a day other than a Saturday,  Sunday or other day on which commercial
banks in New York City are authorized or required by law to close.

Interest
- --------

         The unpaid principal amount of the Bonds of the Twenty-third Series, of
which this Bond is one,  bears  interest at one or more variable  interest rates
per annum  which  rate or rates for each day shall be equal to the rate or rates
per annum borne by the Loans in  accordance  with the Credit  Agreement for such
day  (calculated  in  the  manner  provided  in the  Credit  Agreement  for  the
calculation of interest on the Loans),  payable on each day on which interest is
payable on the Loans in accordance  with the Credit  Agreement (and in an amount
equal to the  Applicable  Share of the amount of interest that is payable on the
Loans on such day in accordance  with the Credit  Agreement)  to the  Collateral
Agent, as the registered owner,  without regard to, or necessity for, any record
date.

Applicable Share
- ----------------

         As used herein,  "Applicable  Share"  means,  as of any day, a fraction
(expressed  as a  percentage  rounded  to the  eighth  decimal  place),  (i) the
numerator  of  which  is the  aggregate  principal  amount  of the  Bonds of the
Twenty-third  Series that are  Outstanding on such day, and (ii) the denominator
of which is the sum of (a) the  aggregate  principal  amount of the Bonds of the
Twenty-third  Series that are  Outstanding  on such day,  plus (b) the aggregate
principal amount of the New Mortgage Bonds,  Credit Agreement (2002) Series, due
2006,  of the Company  (the "South  Dakota  Credit  Agreement  Bonds")  that are
outstanding on such day under the Company's South Dakota Mortgage (as defined in
the Twenty-third Supplemental Indenture).

Redemption
- ----------

         Bonds of the  Twenty-third  Series,  of  which  this  bond is one,  are
subject to redemption  as follows (but shall not otherwise be or become  subject
to  redemption,  whether at the option of the holders  thereof or the Company or
pursuant to any other requirements or provisions of the Indenture):  (A) on each
day on which the Loans are subject to prepayment  in accordance  with the Credit
Agreement, Bonds of the Twenty-third Series shall be subject to redemption in an
aggregate  principal  amount  equal to the  Applicable  Share  of the  aggregate
principal amount of the Loans that are so subject to prepayment on such day; and
(B) on the Acceleration Day, the entire aggregate  principal amount of the Bonds
of the  Twenty-third  Series shall be subject to redemption  (the  "Acceleration
Redemption");  in each case,  without  any  necessity  for notice or call by the
Company or the  Corporate  Trustee  (such  notice  and call being  waived by the
registered  owners of the Bonds of the Twenty-third  Series by the acceptance of
the Bonds of the  Twenty-third  Series and in  connection  with each  Redemption
Demand  (as  hereinafter  defined)).  Redemption  of Bonds  of the  Twenty-third
Series,  of which this bond is one, shall be at a redemption  price equal to the
principal  amount


                                      B-6



of such  Bonds of the  Twenty-third  Series  (without  premium),  together  with
interest  accrued on said  principal  to and  including  the date of  redemption
(collectively,  a  "Redemption  Amount").  In the  event of any  failure  by the
Company to pay when due the Redemption  Amount with respect to any redemption of
Bonds  of  the  Twenty-third  Series,  interest  shall  accrue  on  such  unpaid
Redemption  Amount at the rate or rates (and in amounts equal to the  Applicable
Share of the  amounts)  of  interest  that  accrue on the  corresponding  unpaid
principal of and interest on the Loans in accordance with the Credit Agreement.

         The Corporate  Trustee may  conclusively  presume that no redemption of
Bonds of the  Twenty-third  Series is  required  unless  and until it shall have
received a written  notice  from the  Administrative  Agent,  signed by a person
purporting to be its duly authorized officer, stating that the Loans are subject
to prepayment or have been  accelerated,  in either case, in accordance with the
Credit  Agreement (a "Redemption  Demand").  Each  Redemption  Demand also shall
state the date on which the Loans are subject to prepayment or  acceleration  in
accordance with the Credit Agreement,  the principal amount of the Loans subject
to such  prepayment or  acceleration  on such date, the principal  amount of the
Bonds of the Twenty-third  Series to be redeemed on such date in accordance with
the  Twenty-third  Supplemental  Indenture  by  reason  of  such  prepayment  or
acceleration,  and the  Redemption  Amount payable with respect to such Bonds of
the  Twenty-third   Series  (determined  in  accordance  with  the  Twenty-third
Supplemental  Indenture and setting forth the amounts of the respective portions
thereof representing principal of and interest on such Bonds of the Twenty-third
Series).  Each Redemption Demand shall be accompanied by a written waiver by the
Collateral  Agent, as registered  owner of all of the Bonds of the  Twenty-third
Series then Outstanding,  of notice of redemption and call for redemption by the
Company or the Corporate Trustee of the Bonds of the Twenty-third Series subject
to redemption as described in such Redemption  Demand. The Corporate Trustee may
conclusively  presume the statements  contained in each Redemption  Demand to be
correct.

Additional Terms
- ----------------

         Bonds of the  Twenty-third  Series  shall be subject  to the  following
other terms and conditions:

         (I) For the  avoidance  of any  doubt  (in  the  case of the  following
clauses  (ii)  and  (iii))  and  notwithstanding   anything  herein  or  in  the
Twenty-third Supplemental Indenture to the contrary other than the provisions of
subdivision  (III) below (in the case of the following clause (iii)):  (i) prior
to the Remedy Exercise Day (as hereinafter  defined),  each payment of principal
of or interest  on the Bonds of the  Twenty-third  Series  that  becomes due and
payable  on any day  (whether  by  reason  of  stated  due  date,  acceleration,
redemption or otherwise)  shall  correspond  to, and be equal to the  Applicable
Share of, a payment of  principal  of or interest on the Loans that  becomes due
and payable on such day in  accordance  with the Credit  Agreement;  (ii) on the
Acceleration  Day,  the  Redemption  Amount  with  respect  to the  Acceleration
Redemption shall be due and payable;  and (iii) on and after the Remedy Exercise
Day (as  hereinafter  defined),  (a) the  Redemption  Amount with respect to the


                                      B-7



Acceleration  Redemption  shall bear interest (to the extent permitted by law in
the case of  interest  on the  portion  of the  Redemption  Amount  representing
interest on the  applicable  Bonds) at a variable  rate per annum which rate for
each day shall be equal to the Prime-Based  Rate (as defined in the Twenty-third
Supplemental  Indenture and as calculated by the Corporate Trustee) for such day
plus 6.75%,  payable in the manner  provided in the  Mortgage for the payment of
defaulted interest (including,  without limitation, if applicable, Section 76 of
the Mortgage), and (b) payments of principal of and interest on the Bonds of the
Twenty-third  Series shall cease to  correspond  to payments of principal of and
interest  on the  Loans  (and  shall  not be  satisfied  and  discharged  by the
satisfaction and discharge of the Loans). As used herein,  "Remedy Exercise Day"
means the day (on or after the Acceleration Day) on which all (but not less than
all) of the Bonds of the Twenty-third  Series and all (but not less than all) of
the South Dakota Credit  Agreement Bonds are transferred by the Collateral Agent
to or upon the order of the Lenders in full  satisfaction  and  discharge of the
Loans and the Obligations (as defined in the Collateral  Agreement)  pursuant to
Section 4.1 of the  Collateral  Agreement  (as such transfer is evidenced by the
registration  in the names of the  transferees in such transfer of  certificates
evidencing all (but not less than all) of the Bonds of the  Twenty-third  Series
and all (but not less than all) of the South Dakota Credit Agreement Bonds).

         The Corporate Trustee may conclusively presume that the Remedy Exercise
Day has not occurred  unless and until it shall have  received a written  notice
from  the  Collateral  Agent,  signed  by a  person  purporting  to be its  duly
authorized  officer,  stating that the Remedy  Exercise  Day has  occurred  (the
"Remedy  Exercise  Day  Notice").  The Remedy  Exercise Day Notice (i) shall set
forth the date of the Remedy Exercise Day, (ii) in the case of any such transfer
with  respect to which the  Corporate  Trustee is not the transfer  agent,  have
attached  thereto,  as evidence of the transfer of the Bonds of the Twenty-third
Series  and the  South  Dakota  Credit  Agreement  Bonds  that  gave rise to the
occurrence of the Remedy Exercise Day, copies of certificates  registered in the
names of the  transferees in such transfer of all (but not less than all) of the
Bonds of the  Twenty-third  Series  and all (but not less than all) of the South
Dakota Credit  Agreement  Bonds,  and (iii) if the Remedy Exercise Day Notice is
received by the Corporate  Trustee on a day other than the Remedy  Exercise Day,
the Prime Rate (as defined in the  Supplemental  Indenture)  for each day on and
after the Remedy  Exercise Day and on and prior to the Business Day on which the
Corporate Trustee received the Remedy Exercise Day Notice. The Corporate Trustee
may conclusively  presume the statements in the Remedy Exercise Day Notice to be
correct (and the Corporate Trustee shall be fully protected in relying thereon).

         (II) Prior to the Remedy Exercise Day, the obligation of the Company to
make each payment of  principal of or interest on the Bonds of the  Twenty-third
Series  that  becomes  due and  payable  in  accordance  with  the  Twenty-third
Supplemental  Indenture  (i)  shall be fully  satisfied  and  discharged  if the
corresponding  payment of the  principal  of or interest on the Loans shall have
been fully  paid under and in  accordance  with the Credit  Agreement,  and (ii)
shall be partially satisfied and discharged if the corresponding  payment of the
principal of or interest on the Loans shall have been  partially  paid under and
in accordance with the Credit Agreement (such partial satisfaction and discharge
with respect to


                                      B-8



the Bonds of the Twenty-third  Series to be in an amount equal to the Applicable
Share of the amount of such partial payment with respect to the Loans).

         (III)  Nothing  in  any  of  the  Bonds  of  the  Twenty-third   Series
(including,  without  limitation,  any reference to the  principal  payable with
respect to the Bonds of the Twenty-third Series being determined on the basis of
the Applicable Share of the principal  payable with respect to the Loans) shall,
or shall be deemed or construed to, (i) increase the aggregate  principal amount
of the Bonds of the Twenty-third  Series that are Outstanding from time to time,
(ii)  cause or permit an amount of  principal  of the Bonds of the  Twenty-third
Series  to be or to  become  due and  payable  which,  when  added to all  other
principal of such Bonds theretofore paid, exceeds  $280,000,000,  or (iii) cause
or  permit  to be or to  become  due and  payable  interest  on the Bonds of the
Twenty-third  Series  which is  payable  on any  principal  of the  Bonds of the
Twenty-third  Series  that is in  excess  of the  principal  of the Bonds of the
Twenty-third  Series as  restricted  pursuant to the  preceding  clauses (i) and
(ii).



                                      B-9