Area codes 303, 720, and 983

Area codes 303, 720 and 983 are telephone area codes in the North American Numbering Plan for the north-central portion of the U.S. state of Colorado. The numbering plan area comprises Denver and Boulder, as well as their surrounding suburbs, including Lakewood, Littleton, Longmont, Broomfield, Aurora, and Castle Rock. Area code 303 is the original area code, while area codes 720 and 983 were added (1998, 2022 respectively) to form an overlay complex for the area, meaning that the same geographic service area is served by all area codes and that ten-digit dialing is required for all calls made within the service area.