MDU Resources Group, Inc. operates as a diversified natural resource company in the United States. The company's Electric segment generates, transmits, and distributes electricity in Montana, North Dakota, South Dakota, and Wyoming. As of December 31, 2012, this segment provided its electric services to approximately 131,000 residential, commercial, industrial, and municipal customers in 177 communities and adjacent rural areas. Its Natural Gas Distribution segment distributes natural gas in Montana, North Dakota, South Dakota, and Wyoming, as well as in Idaho, Minnesota, Oregon, and Washington. This segment served approximately 859,000 residential, commercial, and industrial customers in 334 communities and adjacent rural areas. The company's Pipeline and Energy Services segment provides natural gas transportation, underground storage, processing, and gathering services, as well as oil gathering through regulated and nonregulated pipeline systems primarily in the Rocky Mountain and northern Great Plains regions of the United States. This segment also provides cathodic protection and other energy-related services. Its Exploration and Production segment engages in the acquisition, exploration, development, and production of oil and natural gas in the Rocky Mountain and Mid-Continent regions of the United States and in and around the Gulf of Mexico. The company's Construction Materials and Contracting segment mines, aggregates, and markets crushed stone, sand, gravel, and related construction materials, including ready-mixed concrete, cement, asphalt, liquid asphalt, and other value-added products. This segment also provides utility excavation services and inside electrical wiring, cabling, and mechanical services; sells and distributes electrical materials; and manufactures and distributes specialty equipment. MDU Resources Group, Inc. was founded in 1924 and is based in Bismarck, North Dakota.