Organ Pipe Cactus National Monument is a U.S. National Monument and UNESCO biosphere reserve located in extreme southern Arizona which shares a border with the Mexican state of Sonora. The park is the only place in the United States where the Organ Pipe Cactus grows wild. Along with Organ Pipe, many other types of cacti, as well as other desert flora native to the Yuma Desert section of the Sonoran Desert region grow here. The Park is a beautiful preservation of the American Southwest. Organ Pipe Cactus National Monument is 517 square miles (1,338 square kilometers) in size. In 1976 the monument was declared a Biosphere Reserve by UNESCO, and in 1977 95% of Organ Pipe Cactus was declared a wilderness area.