The Peloncillo Mountains and its surrounding valleys, ranges and drainages anchor the center of the Sky Island region—a region of the southwestern United States and northwestern Mexico characterized by isolated mountain ranges separated by desert and grassland. The Peloncillo region is in a unique geographic position that has shaped its rich natural and cultural heritage. It straddles the Arizona and New Mexico boundary in the United States, crosses the international boundary and straddles the Sonora and Chihuahua border in Mexico. The Boundaries of six major biological provinces meet here creating one of the most biologically diverse and productive areas in North America. This region is a sanctuary for many rare, threatened and endangered species and is an important corridor for wildlife movement and migration.