Black Hills Corporation, together with its subsidiaries, operates as a diversified energy company in the United States. The company's Electric Utilities segment generates, transmits, and distributes electricity to approximately 202,000 electric customers in South Dakota, Wyoming, Colorado, and Montana; and distributes natural gas to approximately 35,000 gas utility customers in Cheyenne, Wyoming. It owns 859 Megawatts of generation capacity and 8,530 miles of electric transmission and distribution lines. The company's Gas Utilities segment distributes natural gas to approximately 532,000 natural gas utility customers in Colorado, Nebraska, Iowa, and Kansas. It owns 624 miles of intrastate gas transmission pipelines and 19,979 miles of gas distribution mains and service lines. The company's Oil and Gas segment is involved in the acquisition, exploration, development, and production of crude oil and natural gas primarily in the Rocky Mountain region. This segment's principal assets include the operating interests in the properties in the San Juan basin, the Powder River basin, and the Piceance basin; and non-operated interests in wells located in the Williston, Wind River, Bear Paw Uplift, Arkoma, Anadarko, and Sacramento basins. As of December 31, 2012, it had total reserves of approximately 81 billion cubic feet equivalent of natural gas and crude oil. The company's Power Generation segment produces electric power and sells the electric capacity and energy primarily to other utilities under long-term contracts. Its Coal Mining segment produces coal at its coal mine located near Gillette, Wyoming. The company also provides appliance repair services to approximately 62,000 residential customers; and constructs gas infrastructure facilities for gas transportation customers. Black Hills Corporation was founded in 1941 and is headquartered in Rapid City, South Dakota.