Castle Rock is a home rule municipality that is the county seat of Douglas County, Colorado, United States.The most populous municipality of the county, the community's population was 48,231 at the 2010 United States Census, with an estimated population of 55,747 as of 2014.
The region in and around Castle Rock was originally home to the Arapaho and Cheyenne people. They occupied the land between the Arkansas and South Platte Rivers.White settlers were drawn to the area by rumors of gold and by land opened through the Homestead Act of 1862. However, it was the discovery of rhyolite stone, not gold, that ultimately led to the settlement of Castle Rock.Castle Rock was founded in 1874 when the eastern Douglas County border was redrawn to its present location. Castle Rock was chosen as the county seat because of its central location.