Castle Rock, Colorado Area Code
Castle Rock, CO utilizes an area code overlay in which area codes 303 and 720 serve the same geographic area. Ten digit dialing (area code + seven digit number) is necessary.
In addition to Castle Rock, CO area code information read more about area codes 303 and 720 details and Colorado area codes.
Castle Rock, CO is located in Douglas County and observes the Mountain Time Zone. View our Times by Area Code tool.