The mine was opened in 1977, and operated by
ARCO Coal until it was acquired in 1998 by
Arch Coal. For most of its existence, Black Thunder has been the largest mine in the country (by production), but it was surpassed by the nearby
North Antelope Rochelle Mine. North Antelope Rochelle was created after Peabody Energy purchased the Rochelle mine adjacent to their North Antelope Mine, and consolidated operations. Arch Coal, Inc. announced on March 9, 2009 that it has agreed to purchase Rio Tinto's
Jacobs Ranch mine adjoining Black Thunder, which resulted in Black Thunder once again becoming the largest mine in the world. The operator claims that "Black Thunder's active mine footprint comprises less than 1/4000th of Wyoming's land area", i.e. up to approximately 25 square miles (60 square km), but reclaimed land and as yet undisturbed areas are not included in this figure and much larger. In 2024, Arch Resources announced intention to shrink its operational footprint in Wyoming, with the end goal of eventual closure of these mines. ==Environmental impact==