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 United States Census Bureau estimated the population of Colorado at 5,877,610 as of July 1, 2023, a 1.80% increase since the 2020 United States census.
The region has been inhabited by Native Americans and their ancestors for at least 13,500 years and possibly much longer. The eastern edge of the Rocky Mountains was a major migration route for early peoples who spread throughout the Americas. In 1848, much of the region was annexed to the United States with the Treaty of Guadalupe Hidalgo. The Pike’s Peak Gold Rush of 1858–1862 created an influx of settlers. On February 28, 1861, U.S. President James Buchanan signed an act creating the Territory of Colorado, and on August 1, 1876, President Ulysses S. Grant signed Proclamation 230 admitting Colorado to the Union as the 38th state. The Spanish adjective “colorado” means “colored red” or “ruddy”. Colorado is nicknamed the “Centennial State” because it became a state one century (and four weeks) 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 landscape of mountains, forests, high plains, mesas, canyons, plateaus, rivers, and desert lands. Colorado is one of the Mountain States and is often considered to be part of the southwestern United States. The high plains of Colorado may be considered a part of the midwestern United States.