[EXHIBIT 5(b)-1
                      OPINION OF THELEN REID & PRIEST LLP,
                      COUNSEL TO MDU RESOURCES GROUP, INC.]


                    [LETTERHEAD OF THELEN REID & PRIEST LLP]


                                December 17, 2003



MDU Resources Group, Inc.
Schuchart Building
918 East Divide Avenue
P.O. Box 5650 Bismarck, North Dakota 58506-5650

Ladies and Gentlemen:

     We are acting as counsel for MDU Resources Group, Inc., a Delaware
corporation (the "Company"). We refer to our opinion, dated June 13, 2003 (the
"June 13 Opinion"), addressed to the Company with respect to $500,000,000 in
aggregate amount of (i) debt securities and (ii) common stock, par value $1.00
per share, together with the preference share purchase rights attached thereto,
registered under the Securities Act of 1933, as amended (the "Securities Act"),
on the Registration Statement on Form S-3 (Registration No. 333-104150), as
heretofore amended, which became effective on September 26, 2003 (the
"Registration Statement"). This opinion is supplemental to the June 13 Opinion.

     In connection with this opinion, we have examined originals or copies,
certified or otherwise identified to our satisfaction, of (i) the Registration
Statement, (ii) the prospectus, dated September 26, 2003, forming a part of the
Registration Statement, as supplemented by a prospectus supplement, dated
December 16, 2003, relating to $30.0 million aggregate principal amount of the
Company's 5.98% Senior Notes due 2033 (the "Senior Notes"), (iii) the orders of
the Federal Energy Regulatory Commission, dated November 1, 2002, the Montana
Public Service Commission, dated November 19, 2002, and the Public Service
Commission of Wyoming, dated November 14, 2002 (collectively, the "Orders"),
(iv) the Indenture, dated as of December 15, 2003 (the "Indenture"), between the
Company and The Bank of New York, as Trustee, (v) the form of Officer's
Certificate, to be dated as of December 23, 2003 and (vi) such other
instruments, certificates, records and documents, and such matters of law, as we
have considered necessary or appropriate for the purposes hereof.

     Based on the foregoing, subject to the limitations and qualifications
contained in this opinion, and provided the Orders remain in full force and
effect and have not been amended, rescinded or repealed, we are of the opinion
that:





          1.   The Company is a corporation validly organized and existing under
               the laws of the State of Delaware.

          2.   When the Senior Notes shall have been issued, delivered and
               authenticated in accordance with the terms and provisions of the
               Indenture, the Senior Notes will be legally issued and valid and
               binding obligations of the Company.

     Our opinions expressed above are limited to the law of the State of New
York, the General Corporation Law of the State of Delaware, the applicable
provisions of the Delaware Constitution and the reported judicial decisions
interpreting the Delaware laws and the federal laws of the United States of
America.

     We hereby consent to the use of this opinion as an exhibit to the
Registration Statement and to the use of our name, as counsel, therein. In
giving the foregoing consent, we do not thereby admit that we are in the
category of persons whose consent is required under Section 7 of the Securities
Act or the rules and regulations of the Commission thereunder.

                                               Very truly yours,

                                         /s/ Thelen Reid & Priest LLP

                                           Thelen Reid & Priest LLP