Exhibit 4.1

                       AMENDMENT NO. 1 TO RIGHTS AGREEMENT


     Amendment  No. 1, dated as of  September  24, 2004 to the Rights  Agreement
dated as of March 30, 1999 (the "Agreement"), between KeySpan Corporation (f/k/a
MarketSpan Corporation),  a New York corporation (the "Company"),  and EquiServe
Trust Company, N.A., a national banking association (as successor to The Bank of
New York), as rights agent (the "Rights Agent").

     The Company has approved the  amendment to the  Agreement  set forth below.
Accordingly,  in consideration of the premises and mutual  agreements herein set
forth, the parties hereby agree as follows:

     WHEREAS,  pursuant to Section 27 of the Rights  Agreement,  the Company and
the Rights Agent desire to amend the Rights Agreement as set forth below:

     FIRST:  Section 1(l) of the  Agreement is hereby  deleted and replaced with
the following new language:

"Expiration  Date"  shall  mean the  earliest  of (i) the close of  business  on
September  30, 2004 (the "Final  Expiration  Date"),  (ii) the time at which the
Rights are  redeemed as provided in Section 23 hereof or (iii) the time at which
the Rights are exchanged pursuant to Section 24 hereof. "

     SECOND: This Amendment shall be effective as of the date hereof.

     THIRD:  Except as set forth above,  the  provisions of the Agreement  shall
remain in full force and effect.

     FOURTH: This Amendment shall be deemed to be a contract made under the laws
of the State of New York and for all purposes shall be governed by and construed
in accordance with the laws of such state applicable to contracts to be made and
performed  entirely  within such state.  This  Amendment  may be executed in any
number of  counterparts,  each of such  counterparts  shall for all  purposes be
deemed to be an original,  and all such counterparts  shall together  constitute
but one and the same instrument. If any term, provision, covenant or restriction
of this  Amendment  is  held  by a court  of  competent  jurisdiction  or  other
authority to be invalid, illegal, or unenforceable,  the remainder of the terms,
provisions,  covenants and  restrictions  of this Amendment shall remain in full
force and effect and shall in no way be affected, implied or invalidated.


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     IN WITNESS  WHEREOF,  the parties  hereto have caused this  Agreement to be
duly executed as of the day and year first above written.


KEYSPAN CORPORATION

By: /s/John J. Bishar, Jr.
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Name: John J. Bishar, Jr.
Title: Senior Vice President, General Counsel and Secretary

EQUISERVE TRUST COMPANY, N.A.
as Rights Agent

By: /s/Amelja Regan
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Name: Amelja Regan
Title: Senior Account Manager













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