Castle Rock is a town of approximately 70,000 in central Colorado, 28 miles south of Denver, and 37 miles north of Colorado Springs. It is the county seat and most populous town in Douglas County (in fact, it’s the most populous “town” in the entire state). Douglas County is seeing spectacular growth and has the highest median household income in the state of Colorado, and eighth highest in the United States, and is the richest county not situated in the Northeastern U.S.
Castle Rock was originally inhabited by the Arapaho and Cheyenne people, who occupied the land between the Arkansas and South Platte Rivers. Rumors of gold brought white settlers in the mid-1800s, but the discovery of rhyolite ultimately led to the settling of the town.
Castle Rock is located at 39º22’20″N 104º51’22″W, at an elevation of 6,224 feet, nearly 1,000 feet higher than Denver, the “Mile High City.” It sits at the junction of Interstate 25 and Highway 86. It’s located just east of the Rampart Range of the Rocky Mountains, on the western edge of the Great Plains, just south of Denver’s urban sprawl and north of the Palmer Divide, which separates the town from Colorado Springs. It lies at the heart of the Front Range Urban Corridor, a metropolitan area that stretches from Cheyenne, Wyoming in the north to Pueblo, Colorado in the south, with a total population of about 5 million.
Geographically, the most prominent feature is eponymous Castle Rock, a butte made up of rhyolite which is significantly resistant to erosion. It was formed by a volcanic eruption that took place 37 million years ago, which blanketed the entire area with 20 feet of rhyolite.