We took a sunset drive in the Ajo Mountains of Arizona. This 21-mile loop drive is cactus city! We could hardly believe the volume and variety of cactus—there are 28 species in the preserve.

The national monument is located in the Sonoran Desert along the Mexican border. At the visitor center and start of Ajo Mountain Drive we were 5 miles from the border. We had to stop at two border patrol checkpoints on the way home. Officers peer into your car and ask if everyone is a U.S. citizen. Online, the National Park Service states that visiting Organ Pipe Cactus is safe, though mentions that illegal crossings and drug smuggling occur daily.

The organ pipe cactus is rarely found in the U.S., but common in Mexico. The area protected by the national monument in southern Arizona along the Mexican border is the only area where it grows natively in this country.