SUBSIDIARIES OF MDU RESOURCES GROUP, INC. March 6, 1998 State or Other Jurisdiction in Which Incorporated Alaska Basic Industries, Inc. Alaska Anchorage Sand and Gravel Company, Inc. Alaska Baldwin Contracting Company, Inc. California Centennial Energy Holdings, Inc. Delaware Concrete, Inc. California Fidelity Oil Co. Delaware Fidelity Oil Holdings, Inc. Delaware High Line Equipment, Inc. Delaware ILB Hawaii, Inc. Hawaii International Line Builders, Inc. Delaware Knife River Corporation Delaware Knife River Dakota, Inc. Delaware Knife River Hawaii, Inc. Delaware Knife River Marine, Inc. Delaware KRC Aggregate, Inc. Delaware KRC Holdings, Inc. Delaware LTM, Incorporated Oregon Medford Ready Mix, Inc. Delaware Morse Bros., Inc. Oregon Prairie Propane, Inc. Delaware Prairielands Energy Marketing, Inc. Delaware Rogue Aggregates, Inc. Oregon S2 - F Corp. Oregon Utility Services, Inc. Delaware WBI Canadian Pipeline, Ltd. Canada Williston Basin Interstate Pipeline Company Delaware