Black Hills Corporation, through its subsidiaries, operates as a vertically-integrated utility company in the United States. The company's Electric Utilities segment generates, transmits, and distributes electricity to approximately 208,500 electric customers in South Dakota, Wyoming, Colorado, and Montana. This segment owns 941 megawatts of generation capacity and 8,806 miles of electric transmission and distribution lines. Its Gas Utilities segment distributes natural gas to approximately 1,030,800 natural gas utility customers in Arkansas, Colorado, Iowa, Nebraska, Kansas, and Wyoming. This segment owns 4,585 miles of intrastate gas transmission pipelines and 40,044 miles of gas distribution mains and service lines. The company's Power Generation segment produces electric power and sells the electric capacity and energy primarily to its utilities under long-term contracts. Its Mining segment produces coal at its coal mine located near Gillette, Wyoming and sells the coal to electric generation facilities. The company's Oil and Gas segment explores, develops, and produces 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 various states. As of December 31, 2016, it had total reserves of approximately 78 billion cubic feet equivalent of natural gas, crude oil, and natural gas liquids. Black Hills Corporation also provides appliance repair services to approximately 61,000 residential customers; and constructs gas infrastructure facilities and electrical systems for gas transportation and electric utilities customers. The company was founded in 1941 and is headquartered in Rapid City, South Dakota.