Colorado is a state in the Mountain West subregion of the Western United States. It encompasses 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 the eighth most extensive and 21st most populous U.S. state. The 2020 United States Census enumerated the population of Colorado at 5,773,714, an increase of 14.80% 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. "Colorado" is the Spanish adjective meaning "ruddy," the color of red sandstone. 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.