Contours, elevations and trails from OpenTopoMap. Scroll down for the zoomable map.
Grand Canyon National Park in Arizona protects a mile-deep, 277-mile-long gorge carved by the Colorado River over millions of years. Its layered walls of red and ochre rock record nearly two billion years of geology, best seen from the South Rim.
Theodore Roosevelt declared the canyon a national monument in 1908 after Congress repeatedly failed to protect it. It didn't formally become a national park until 1919.
