Kofa National Wildlife Refuge was established in 1939. The refuge encompasses 665,400 acres of pristine desert that is home to the desert bighorn sheep and the California fan palm, the only native palm in Arizona. Bighorn sheep are found chiefly in the two mountain ranges that dominate the refuge landscape - the Kofa and Castle Dom Mountains. Although these mountains are not especially high, they are extremely rugged and rise sharply from the surrounding desert plains, providing excellent bighorn sheep habitat. A wide variety of plant life is found throughout the refuge.