Although there are arches and natural bridges found all over the world, these natural phenomena nowhere are found in such profusion as they are in Arches National Park, located in Grand County, Utah, north of the town of Moab. The Colorado River forms the southern boundary of the park, and the LaSal Mountains are visible from most viewpoints inside the park`s boundaries. The park is situated in the middle of the Colorado Plateau, a vast area of deep canyons and prominent mountain ranges that also includes Canyonlands National Park, Colorado National Monument, Natural Bridges National Monument, and Dinosaur National Monument. The Colorado Plateau is covered with layers of Jurassic-era sandstones; the type most prevalent within the Park is called Entrada Sandstone, a type that lends itself to the arch cutting that gives the park its name.
Arches National Park covers more than 73,000 acres, or about 114 square miles. There are more than 500 arches found inside the park's boundaries, and the possibility exists that even more may be discovered. The concentration of arches within the park is the result of the angular topography, much exposed bare rock, and erosion on a major scale. In such an arid area - annual precipitation is about 8.5 inches per year - it is not surprising that the agent of most erosion is wind and frost.