Denver is the capital and the most populous city of Colorado, in the United States. Denver is a consolidated city-county located in the South Platte River Valley on the High Plains just east of the Front Range of the Southern Rocky Mountains. The Denver downtown district is located immediately east of the confluence of Cherry Creek with the South Platte River, approximately 15 miles (24 km) east of the foothills of the Rocky Mountains. Denver is nicknamed the Mile-High City because its official elevation is exactly one mile, or 5,280 feet (1,609 m) above sea level. The 105th meridian west of Greenwich passes through Union Station, making it the reference point for the Mountain Time Zone.
The United States Census Bureau estimates that the population of the City and County of Denver was 588,349 on July 1, 2007, making it the 26th most populous U.S. city. The 5-county Denver-Aurora Metropolitan Statistical Area had an estimated 2007 population of 2,464,866 and ranked as the 21st most populous U.S. metropolitan statistical area, and the 12-county Denver-Aurora-Boulder Combined Statistical Area had an estimated 2007 population of 2,998,878 and ranked as the 17th most populous U.S. metropolitan area. The 18-county Front Range Urban Corridor had an estimated 2007 population of 4,166,855. It is also the second largest city in the Mountain West after Phoenix. The city has the 10th largest central business district in the United States.