CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO SECTION 906

OF THE SARBANES-OXLEY ACT OF 2002

    Each of the undersigned, Brian R. Gray, the President and Chief Executive Officer, and Nathan W. Ring, the Vice President and Chief Financial Officer of Knife River Holding Company (the "Company"), DOES HEREBY CERTIFY that:

    1.  The Company's Quarterly Report on Form 10-Q for the quarter ended March 31, 2023 (the "Report"), fully complies with the requirements of Section 13(a) of the Securities Exchange Act of 1934; and

    2.  Information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

    IN WITNESS WHERE OF, each of the undersigned has executed this statement this 16th day of May, 2023.

/s/ Brian R. Gray

Brian R. Gray

President and Chief Executive Officer

/s/ Nathan W. Ring

Nathan W. Ring

Vice President and Chief Financial Officer

A signed original of this written statement required by Section 906 has been provided to Knife River Holding Company and will be retained by Knife River Holding Company and furnished to the Securities and Exchange Commission or its staff upon request.