Colorado (, other variants) is a state in the western United States 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. It is the 8th most extensive and 21st most populous U.S. state. The estimated population of Colorado is 5,758,736 as of 2019, an increase of 14.5% since the 2010 United States Census.

The region has been inhabited by Native Americans for more than 13,000 years, with the Lindenmeier Site containing artifacts dating from approximately 9200 BCE to 1000 BCE; the eastern edge of the Rocky Mountains was a major migration route for early peoples who spread throughout the Americas. The state was named for the Colorado River, which early Spanish explorers named the Río Colorado (“Red River”) for the ruddy silt the river carried from the mountains. The Territory of Colorado was organized on February 28, 1861, and on August 1, 1876, U.S. President Ulysses S. Grant signed Proclamation 230 admitting Colorado to the Union as the 38th state. Colorado is nicknamed the “Centennial State” because it became a state one century after the signing of the United States Declaration of Independence.

Colorado is bordered by Wyoming to the north, Nebraska to the northeast, Kansas to the east, Oklahoma to the southeast, New Mexico to the south, Utah to the west, and touches Arizona to the southwest at the Four Corners. Colorado is noted for its vivid landscape of mountains, forests, high plains, mesas, canyons, plateaus, rivers and desert lands. Colorado is one of the Mountain States and is a part of the western and southwestern United States.

Denver is the capital and most populous city in Colorado. Residents of the state are known as Coloradans, although the antiquated term “Coloradoan” is occasionally used. Colorado is a comparatively wealthy state, ranking 8th in household income in 2016, and 11th in per capita income in 2010. Major parts of the economy include government and defense, mining, agriculture, tourism, and increasingly other kinds of manufacturing. With increasing temperatures and decreasing water availability, Colorado’s agriculture, forestry and tourism economies are expected to be heavily affected by climate change.