High Quality Content by WIKIPEDIA articles! Wall Arch was a natural sandstone arch in the Arches National Park in the U.S. state of Utah. Before its collapse in 2008, it was ranked 12th in size among the park`s over 2,000 arches. At its largest, the opening underneath the span was 71 feet (22 m) wide by 33.5 feet (10 m) high. It consisted of Entrada Sandstone, specifically the member known as Slick Rock. Wall Arch was first reported and named in 1948 by Lewis T. McKinney.