A river of the southwest United States rising in the Rocky Mountains and flowing about 2,333 km (1,450 mi) southwest through the Colorado Plateau of western Colorado, southeast Utah, and western Arizona to the Gulf of California in northwest Mexico. In Arizona it flows along the borders of Nevada and California. The most spectacular of its many gorges is the Grand Canyon.
The Grand Canyon became a U.S. National Monument on this date in 1908. Its valley system, the world’s largest, was created by erosion from the Colorado River. The huge gorge which makes up the Grand Canyon is approximately 1 mi/1.6 km deep; its width ranges from 4-18 mi/6.4-29 km; and it runs some 280 mi/450 km from Marble Canyon, near the Arizona-Utah border, to Grand Wash Cliffs in Arizona’s northern Mohave County. In 1919, the 1.2-million-acre/492,000-hectare Grand Canyon National Park was created by an Act of Congress. Some five million visitors make their way to the Grand Canyon each year. The South Rim is the more accessible and more popularly-traveled area of the park. According to the National Park Service website, there are several major ecosystems contained in the area, and more than 1,500 plant, 355 bird, 89 mammalian, 47 reptilian, 9 amphibian, and 17 fish species are found there.