Hart Mountain National Antelope Refuge, established in 1936 on Hart Mountain in southeastern Oregon, began as a sanctuary for remnant pronghorn herds and has grown into a vast high-desert refuge protecting more than 422 square miles of native wildlife habitat. Its sagebrush flats, rocky cliffs, playa lakes, and spring-fed meadows support more than 300 species, including pronghorn, bighorn sheep, mule deer, sage grouse, trout, and many birds. A major turning point came when cattle grazing was banned in 1994 after habitat damage; later studies recorded recovering riparian areas and the return of native vegetation, helping preserve one of the region’s largest undeveloped wildlife landscapes without domestic livestock.