Located in Arches National Park in Utah Landscape Arch a natural arch created from the erosion of sandstone.
Discovered in late 1933 or early 1934 by Frank Beckwith, Landscape Arch is one of many in an area know as 'Devil's Garden' but has the honor of being the world's longest arch with a confirmed span of 290 feet or does it...
Even if it does hold the title, Landscape Arch may not hold it much longer. In the last 15 years major chucks have fallen off the arch and in some places it is only 6 feet thick, thus is expected to eventually collapse.
Kolob Arch is located in Zion National Park, also in Utah, but problems arise when determining how to measure the span. It is, however, generally accepted to be 294 feet, beating out Landscape Arch by a mere 4 feet as the world's longest arch.