Colorado is the 38th state of the United States of America, admitted to the Union on August 1, 1876.

The Rocky Mountains, or Rockies, form the most dominant physical feature of the state. To the West of the Rockies lie the high plateaus of the Colorado Plateau, and to the East are the Great Plains. High, rugged mountains and plateaus occupy fully two-thirds of the state and make Colorado a state of striking beauty.

All of Colorado is more than 1,000 m (3,300 ft) above sea level. The state, with an average elevation of 2,070 m (6,800 ft), is the highest of all the states.

The mountains and plateaus are rich in gold, silver, and other minerals and are the source of most of the state’s water.

The mountains have played a major role in the development of Colorado, most recently by attracting a steady flow of tourists, but they have also been a barrier to travel, communication, and settlement. Except for small cities and towns in the sheltered river valleys and mountain basins, most of Western Colorado is sparsely populated.

In contrast, Eastern Colorado has flat, treeless plains that extend from the Rockies to the Nebraska and Kansas state lines. Cultivated where there is sufficient moisture or irrigation, they consist of croplands and grasslands.

On the plains just East of the Rockies is Denver, which is the state capital, the center of the state’s largest metropolitan area, and a major city of the Western United States.

The state’s name is a Spanish word meaning "reddish colored". It was the name early Spanish explorers gave to the Colorado River, which originates in the state. When Colorado became a territory in 1861, William Gilpin, the first territorial governor, formally requested that it be called by the old Spanish name.

Colorado was admitted to statehood during the 100th anniversary of the signing of the Declaration of Independence, and today its official nickname is the Centennial State.

Most of Colorado’s major cities lie at the foot of the Rockies. Following are the state’s principal urban areas, in order of population (US Census 2006 estimates).

• Denver, located on the South Platte River in North central Colorado, is the state’s capital and largest city, the leading industrial and commercial center, and a popular recreation center.
• Colorado Springs, the seat of El Paso County, is primarily a residential, light industrial, and resort city in central Colorado. Nearby are the United States Air Force Academy, the headquarters of the North American Air Defense Command, and Fort Carson, a major United States Army post.
• Aurora, in Arapahoe, Adams and Douglas counties in central Colorado, is the principal suburb in the Denver-Aurora Metropolitan Area.

Other major Colorado cities include

• Lakewood, in Jefferson County, a community in the Denver metropolitan region at the base of the Rocky Mountain foothills in central Colorado.
• Fort Collins, the seat of Larimer County, an important agricultural and tourist region in northern Colorado.
• Thornton, in Adams County, primarily a residential city near Denver in northern Colorado, with some light industry.
• Westminster, in Adams and Jefferson counties, a commercial center and residential community in north central Colorado, near Denver.
• Pueblo, the seat of Pueblo County, an important industrial city in central Colorado and the location of several federal offices, including a branch of the Government Printing Office.

Other notable cities include

• Centennial, a recently incorporated city from portions of unincorporated Arapahoe County.
• Boulder, the seat of Boulder County, an educational and research center just NorthWest of Denver, home to the largest campus of the University of Colorado and the National Center for Atmospheric Research.
• Greeley, the seat of Weld County, a rich agricultural area in northern Colorado that produces livestock, sugar beets, and potatoes.
• Longmont, in Boulder County, offers urban culture, natural beauty and small town charm at the foot of the Rocky Mountains in northern Colorado.