Rio Tinto Energy America (RTEA) was a wholly owned American subsidiary of the England and Australia-based mining giant, the Rio Tinto Group, headquartered in Gillette, Wyoming, United States. The company, previously known as Kennecott Energy after another of Rio Tintos American subsidiaries, was formed in 1993 when Rio Tinto purchased NERCO and placed that companys Spring Creek coal mine and Antelope coal mine under the RTEA umbrella. Subsequent acquisitions included the Cordero Mining Company, the Colowyo Coal Company, and the Jacobs Ranch coal mine. RTEA operated four mines in Wyoming and Montana, supplying fuel for the generation of approximately 6% of the United States' electricity consumption. The RTEA mines were spun off to Cloud Peak Energy in 2010. In November 2007, Rio Tinto Group announced that it would try to divest RTEA and its assets. As a first step in that effort, Rio Tinto agreed in March 2009 to sell the Jacobs Ranch coal mine to Arch Coal for a sum of $761 million. In December 2010, Rio Tinto announced that it had succeeded in "100 per cent divestment of its equity holdings in Cloud Peak Energy Inc. through a fully exercised over allotment in connection with a recently announced secondary offering." Cloud Peak Energy stated that the result of the divestment was that Cloud Peak Energy Resources LLC "is now a wholly owned subsidiary of Cloud Peak Energy Inc."