| Subsidiaries | Jurisdiction of Formation | ||||
Alaska Basic Industries, Inc. | Alaska | ||||
| Ames Sand & Gravel, Inc. | North Dakota | ||||
| Anchorage Sand and Gravel Company, Inc. | Alaska | ||||
| ARC Fabricators, L.L.C. | South Dakota | ||||
| Baldwin Contracting Company, Inc. | California | ||||
| Bell Electrical Contractors, Inc. | Missouri | ||||
| Bombard Electric, LLC | Nevada | ||||
| Bombard Mechanical, LLC | Nevada | ||||
| Capital Electric Construction Company, Inc. | Kansas | ||||
| Capital Electric Line Builders, Inc. | Kansas | ||||
| Cascade Natural Gas Corporation | Washington | ||||
| Centennial Energy Holdings, Inc. | Delaware | ||||
| Centennial Holdings Capital LLC | Delaware | ||||
| Central Oregon Redi-Mix, LLC | Oregon | ||||
| Concrete, Inc. | California | ||||
| Connolly-Pacific Co. | California | ||||
| D S S Company | California | ||||
| Desert Fire Holdings, Inc. | Nevada | ||||
| Desert Fire Protection, a Nevada Limited Partnership | Nevada | ||||
| Desert Fire Protection, Inc. | Nevada | ||||
| Desert Fire Protection, LLC | Nevada | ||||
| Duro Electric Company | Colorado | ||||
| E & ER Company | South Dakota | ||||
| Ellis & Eastern Company | South Dakota | ||||
| E.S.I., Inc. | Ohio | ||||
| Fairbanks Materials, Inc. | Alaska | ||||
| Fidelity Exploration & Production Company | Delaware | ||||
| Frebco, Inc. | Ohio | ||||
| FutureSource Capital Corp. | Delaware | ||||
| Granite City Ready Mix, Inc. | Minnesota | ||||
| Hawaiian Cement | Hawaii | ||||
| Intermountain Gas Company | Idaho | ||||
| International Line Builders, Inc. | Delaware | ||||
| InterSource Insurance Company | Vermont | ||||
| Jebro Incorporated | Iowa | ||||
| JTL Group, Inc. (Montana corporation) | Montana | ||||
| JTL Group, Inc. (Wyoming corporation) | Wyoming | ||||
| Kent’s Oil Service | California | ||||
| Knife River Corporation | Delaware | ||||
| Knife River Corporation - Mountain West | Delaware | ||||
| Knife River Corporation – North Central | Minnesota | ||||
| Knife River Corporation – Northwest | Oregon | ||||
| Knife River Corporation – South | Texas | ||||
| Knife River Dakota, Inc. | Delaware | ||||
| Knife River Hawaii, Inc. | Delaware | ||||
| Knife River Holding Company | Delaware | ||||
| Knife River Marine, Inc. | Delaware | ||||
| Knife River Midwest, LLC | Delaware | ||||
| KRC Holdings, Inc. | Delaware | ||||
| Lone Mountain Excavation & Utilities, LLC | Nevada | ||||
| Loy Clark Pipeline Co. | Oregon | ||||
| LTM, Incorporated | Oregon | ||||
| MDU Construction Services Group, Inc. | Delaware | ||||
| MDU Energy Capital, LLC | Delaware | ||||
| MDU Industrial Services, Inc. | Delaware | ||||
| MDU United Construction Solutions, Inc. | Delaware | ||||
| Montana-Dakota Utilities Co. | Delaware | ||||
| Northstar Materials, Inc. | Minnesota | ||||
| OEG, Inc. | Oregon | ||||
| PerLectric, Inc. | Virginia | ||||
| Prairie Cascade Energy Holdings, LLC | Delaware | ||||
| Prairie Intermountain Energy Holdings, LLC | Delaware | ||||
| Rail to Road, Inc. | South Dakota | ||||
| Rocky Mountain Contractors, Inc. | Montana | ||||
| Sweetman Const. Co. | South Dakota | ||||
| USI Industrial Services, Inc. | Delaware | ||||
| Wagner Group, Inc., The | Delaware | ||||
| Wagner-Smith Company, The | Ohio | ||||
| Wagner-Smith Equipment Co. | Delaware | ||||
| WBI Canadian Pipeline, Ltd. | Canada | ||||
| WBI Energy Midstream, LLC | Colorado | ||||
| WBI Energy Transmission, Inc. | Delaware | ||||
| WBI Energy, Inc. | Delaware | ||||
| WBI Holdings, Inc. | Delaware | ||||
| WHC, Ltd. | Hawaii | ||||