ORGAN PIPE CACTUS NATIONAL MONUMENT

national monument in southwestern Arizona, U.S., at the Mexican border, 12 miles (19 km) south of Ajo. Established in 1937 with an area of 517 square miles (1,339 square km), it preserves segments of the mountainous Sonoran Desert and is named for the organ-pipe cactus (found in the United States only in this locality and so called because its branches resemble organ pipes). Desert ironwood, ocotillo, and numerous other desert plants are also found there. Wildlife includes the venomous lizards known as Gila monsters, pronghorn antelope, coyotes, and a variety of birds. Portions of El Camino del Diablo (Devil's Highway), the historic Spanish route along which hundreds of miners and pioneers lost their lives, may still be seen.