Sierra Madre, a casino town near the Grand Canyon, was used as a testing ground by the chemical company Big MT with the aid of industrialist Frederick Sinclair. After a harmful toxin leaked into the atmosphere, Big MT provided bulky hazmat suits to its workers, difficult to move or speak in, and - as it turned out - ineffective at protecting from the gas. After the Great War, the workers were stranded in Sierra Madre and were forced to extreme measures to survive, becoming feral hunters.