387-7742, 387-6849, off AZ Hwy. 85, south of Ajo, AZ. $8/vehicle, valid for one week. Open 24 hours. Visitor center 8 a.m.–5 p.m.This national monument was established to protect the unique organ pipe cactus and its Sonoran Desert habitat. The monument supports 26 other species of cactus as well as a multitude of wildlife. Many species are nocturnal.