 Denver ( / ˈdɛnvər / ) , officially the City and County of Denver , is the capital and most populous municipality of the U.S. state of Colorado . Denver is located in the South Platte River Valley on the western edge of the High Plains just east of the Front Range of the Rocky Mountains . The Denver downtown district is located immediately east of the confluence of Cherry Creek with the South Platte River , approximately 12 mi ( 19 km ) east of the foothills of the Rocky Mountains . Denver is nicknamed the Mile @-@ High City because its official elevation is exactly one mile ( 5 @,@ 280 ft or 1 @,@ 610 m ) above sea level , making it one of the highest major cities in the United States . The 105th meridian west of Greenwich , the longitudinal reference for the Mountain Time Zone , passes directly through Denver Union Station . 
