After its first bid for statehood was vetoed by President Andrew Johnson, Colorado entered the Union on August 1, 1876, the year the United States celebrated its centennial. Thus, the thirty-eighth state is known as the Centennial State.
Among the early inhabitants of the land encompassed by Colorado were the Anasazi cliff dwellers. They were forced by drought and other factors to abandon their Mesa Verde homes in the late 1200s. At the time of European exploration and settlement Colorado's population was made up of Arapaho, Cheyenne, and Ute peoples. Their territory was explored by the Spanish who, after Napoleon's conquest of Spain, turned over its title to the French.
The United States acquired the eastern part of Colorado in 1803 through the Louisiana Purchase and the western portion in 1848 through the Treaty of Guadalupe Hidalgo. In 1850, the federal government also purchased a Texas claim in Colorado. This combined property eventually became the Colorado Territory in 1861.