The City of Castle Pines is statutory city located in Douglas County, Colorado, United States. As of the 2010 census, the population of the city was 10,360. By 2013, the United States Census Bureau estimated the population to have increased to 10,726. The city is situated 19 miles (31 km) south-southeast of the Colorado State Capitol in Denver. The city is located north of the Town of Castle Rock and south of the City of Lone Tree, Colorado.