Castle Rock, Colorado in the context of Castle Rock (Colorado)

The U.S. State of Colorado has 273 active municipalities, comprising 198 towns, 73 cities, and two consolidated city and county governments. The City and County of Denver, the state capital, is the oldest municipality in Colorado. On December 3, 1859, the extralegal Territory of Jefferson granted a charter to the consolidated City of Denver, Auraria, and Highland. The Town of Keystone, incorporated on February 8, 2024, is the newest Colorado municipality.

Colorado municipalities range in population from the City and County of Denver with a 2020 population of 715,522, to the Town of Carbonate, which has had no year-round population since the 1890 Census due to its severe winter weather and difficult access. The City of Black Hawk with a 2020 population of 127 is the least populous Colorado city, while the Town of Castle Rock with a 2020 population of 73,158 is the most populous Colorado town.

Douglas County is a county located in the U.S. state of Colorado. As of the 2020 Census, the population was 357,978. The county is named in honor of U.S. Senator Stephen A. Douglas. The county seat is Castle Rock.

Douglas County is part of the Denver metropolitan area. It is located midway between Colorado's two largest cities, Denver and Colorado Springs, and contains a portion of Aurora, the state's third-largest city. Douglas County has the highest median household income of any Colorado county or statistical equivalent. It is ranked seventh nationally in that category.