<P> Arches National Park is a national park in eastern Utah, United States . The park is adjacent to the Colorado River, 4 miles (6 km) north of Moab, Utah . More than 2,000 natural sandstone arches are located in the park, including the well - known Delicate Arch, as well as a variety of unique geological resources and formations . The park 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 on the Colorado Plateau . The highest elevation in the park is 5,653 feet (1,723 m) at Elephant Butte, and the lowest elevation is 4,085 feet (1,245 m) at the visitor center . The park receives an average of less than 10 inches (250 mm) of rain annually . </P> <P> Administered by the National Park Service, the area was originally named a national monument on April 12, 1929, and was redesignated as a national park on November 12, 1971 . The park is expected to receive 1.8 million visitors in 2018 . </P> <P> The national park lies above 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 become a national park