Cordero Rojo Mine Complex, Wyoming

The Cordero and Caballo Rojo mines were merged in 1997 to create one of the largest and most productive coal mines in the United States. Initially operated by Rio Tinto Energy America, the mine was purchased by Cloud Peak Energy in 2010. The operation spans 6,500 acres of Bureau of Land Management land, estimated to contain around 350 million more tons of coal. The extraction rate varies between 30 to 40 million tons per year.