The Salt Plains National Wildlife Refuge is part of the United States system of national wildlife refuges. It is located in Alfalfa County in northern Oklahoma, north of Jet (pop. 230), along Great Salt Plains Lake, which is formed by a dam on the Salt Fork of the Arkansas River. The refuge was established March 26, 1930, by executive order of President Herbert Hoover, and contains 32,080 acres (130 km2) of protected land as habitat to about 312 species of birds and 30 species of mammals. It was designated a national natural landmark in June 1983.