Organ Pipe Cactus National Monument in Arizona protects spectacular wilderness in the heart of the Sonoran Desert. The park is the only place in the United States where visitors can see large stands of organ pipe cacti, which can live to be more than 150 years old. Explore this Southwest gem with activities like hiking, camping, wildflower walks, scenic drives and night sky gazing. Sunset photo by Jim Dunham. Posted on Tumblr by the US Department of the Interior, 7/28/16.