The Grand Canyon is a very colorful, steep-sided gorge, carved by the Colorado River, in northern Arizona, USA. The canyon appears on many versions of the Seven Natural Wonders of the World list, although none of these lists is by any means authoritative. It is largely contained within the Grand Canyon National Park — one of the first national parks in the United States. President Theodore Roosevelt was a major proponent of the Grand Canyon area, visiting on numerous occasions to hunt mountain lions and enjoy the scenery.

The Canyon, created by the Colorado River cutting a channel over millions of years, is about 277 miles (446 km) long, ranges in width from 0.25 to 15 miles (0.4 to 24 kilometers) and attains a depth of more than a mile (1,600 m). Nearly two billion years of the Earth's history has been exposed as the Colorado River and its tributaries cut through layer after layer of sediment as the Colorado Plateaus have uplifted.

The first recorded sighting of the Grand Canyon by a European was in 1540, García López de Cárdenas from Spain.[citation needed] The first scientific expedition to the canyon was led by U.S. Major John Wesley Powell in the late 1860s. Powell referred to the sedimentary rock units exposed in the canyon as "leaves in a great story book." However, long before that, the area was inhabited by Native Americans who built settlements within the canyon walls.