Organ Pipe Cactus National Monument (ORPI) was established by President Franklin Delano Roosevelt in 1937, and named for a cactus rarely found in the United States. This monument celebrates the life and landscape of the Sonoran Desert in an almost pristine setting. It is a true wilderness where plants and animals live amid dramatic scenery. Sharp volcanic mountains and rocky canyons slope down to forbiddingly hot lowland plains. In this setting you may drive a lonely road, hike a backcountry trail, camp under a clear sky, enjoy the fathomless the night sky, or just soak up the warmth and beauty of the Southwest.
Organ Pipe Cactus has dramatic scenery. In the Ajo Mountains along the eastern boundary is Mount Ajo, at 4808 ft the highest elevation in the monument. Land gradually slopes to the southwest and ends in a series of low plains at less than 1000 feet elevation. In between is classic basin-and-range topography. Mountains reveal their volcanic history in colorful bands or chunks of lavas. As these mountains erode, they form coalescing alluvial vans, or bajadas. Soil and moisture conditions on these bajadas create the ideal habitat for warmth-loving Sonoran Desert plant and animal species. On these slopes you will find the greatest biodiversity within the monument including stands of organ pipe, saguaro, and other cactus species. Here is also the greatest concentration of wildlife from mountain lion to javelina, coyote to grasshopper mouse to desert tortoise. Valley floors are covered with widely spaced creosote bushes and salt-tolerant plants. Frost-free areas are home to senita cactus, the third of only three native columnar cactus species found north of Mexico.
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