MDU Resources has branched out from its roots as a regional utility to cover a range of natural resources businesses. Utility subsidiaries Montana-Dakota Utilities, Wyoming Utilities Great Plains Natural Gas and Cascade Natural Gas, deliver gas to more than 906,000 customers and electricity to more than 142,000 customers in 177 communities. MDU Resources' energy business is focused on natural gas transmission, gathering, and storage. The company also has an oil refinery business. Its construction materials and contracting division (including Knife River) mines and sells concrete, gravel, and other materials. MDU Resources' MDU Construction Services unit builds power lines, pipelines, and telecom systems.