Colorado (i/kɒləˈrædoʊ/, or /kɒləˈrɑːdoʊ/) is a U.S. state encompassing most of the Southern Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains. Colorado is part of the Western United States, the Southwestern United States, and the Mountain States. Colorado is the 8th most extensive and the 22nd most populous of the 50 United States. The United States Census Bureau estimates that the population of Colorado was 5,187,582 on July 1, 2012, an increase of +3.15% since the 2010 United States Census.
The state was named for the Colorado River, which Spanish explorers named the Río Colorado for the ruddy (Spanish: colorado) silt the river carried from the mountains. On August 1, 1876, U.S. President Ulysses S. Grant signed a proclamation admitting Colorado to the Union as the 38th state. Colorado is nicknamed the "Centennial State" because it became a state in the centennial year of the United States Declaration of Independence.
Colorado is bordered by the northwest state of Wyoming to the north, the Midwest states of Nebraska and Kansas to the northeast and east, on the south by New Mexico and Oklahoma, on the west by Utah, and Arizona to the southwest. The four states of Colorado, New Mexico, Utah, and Arizona meet at one common point known as the Four Corners, which is known as the heart of the American Southwest. Colorado is noted for its vivid landscape of mountains, forests, high plains, mesas, canyons, plateaus, rivers, and desert lands.
Denver is the capital and the most highly populated city of Colorado. Residents of the state are properly known as "Coloradans", although the archaic term "Coloradoan" is still used