<P> Arches National Park is a United States National Park in eastern Utah . The park is adjacent to the Colorado River, 4 miles (6 km) north of Moab, Utah . It is home to over 2,000 natural sandstone arches, including the world - famous Delicate Arch, in addition to a variety of unique geological resources and formations . It contains the highest density of natural arches in the world . </P> <P> The park consists of 76,679 acres (119.811 sq mi; 31,031 ha; 310.31 km) of high desert located in the Colorado Plateau . Its highest elevation is 5,653 feet (1,723 m) at Elephant Butte, and its lowest elevation is 4,085 feet (1,245 m) at the visitor center . Forty - three arches are known to have collapsed since 1977 . The park receives on average 10 inches (250 mm) of rain a year . </P> <P> Administered by the National Park Service, the area was originally named a National Monument on April 12, 1929 . It was redesignated as a National Park on November 12, 1971 . </P> <P> The national park lies atop an underground evaporite layer or salt bed, which is the main cause of the formation of the arches, spires, balanced rocks, sandstone fins, and eroded monoliths in the area . This salt bed is thousands of feet thick in places, and was deposited in the Paradox Basin of the Colorado Plateau some 300 million years ago when a sea flowed into the region and eventually evaporated . Over millions of years, the salt bed was covered with debris eroded from the Uncompahgre Uplift to the northeast . During the Early Jurassic (about 210 Ma) desert conditions prevailed in the region and the vast Navajo Sandstone was deposited . An additional sequence of stream laid and windblown sediments, the Entrada Sandstone (about 140 Ma), was deposited on top of the Navajo . Over 5,000 feet (1,500 m) of younger sediments were deposited and have been mostly eroded away . Remnants of the cover exist in the area including exposures of the Cretaceous Mancos Shale . The arches of the area are developed mostly within the Entrada formation . </P>

When did arches national park became a national park