Area codes 303 and 720 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, Aurora, and Castle Rock. Area code 303 is the original area code, while area code 720 was added to form an overlay plan for the area, meaning that the same geographic service area is served by both area codes and that ten-digit dialing is required for all calls made within the service area.
Area code 303 was one of the original North American area codes of 1947, when it was assigned for service of the entire state of Colorado for forty years, despite Colorado's growth during the second half of the 20th century, especially in the Denver area. By the late 1980s, an impending number shortage made a split necessary. On March 5, 1988, southeastern Colorado, including Colorado Springs and Pueblo, received area code 719. The northeastern and western portions of area code 303, including Fort Collins, Grand Junction, Vail and Aspen, switched to area code 970 on April 2, 1995, reducing 303 to the Denver-Boulder area. With the 1995 split, 303 was the only Colorado area code that did not border another state.
Although the 1995 split was intended as a long-term solution, the area continued to experience sharp growth so that within two years, further relief was necessary. The Front Range is home not only to most of Colorado's landlines, but also most of the state's cell phones, fax machines, and pagers. On September 1, 1998, area code 720 was activated in the 303 service area to create an overlay.
The Denver metropolitan area is expected to reach exhaustion levels again by 2023, according to official projections in 2020.
The 303/720 area is one of the largest toll-free calling zones in the western United States. With the exception of Roggen, Brighton, and Wiggins, no long-distance charges are applied to any calls made from one phone to another in the area.
With the exception of Roggen, all users in the 303/720 area must dial all ten digits to reach a destination subscriber.
- "Area Codes Map, Colorado". NANPA. Retrieved April 24, 2018.
- NANP Information Letter 87-03-045 (1987-03-27), retrieved 2020-08-29
- NANPA Information Letter 94/09-012 (1994-09-21) retrieved 2020-08-29
- MICHAEL LOVELL (August 31, 1998). "10-Digit Dialing Hits Denver Area". Reuters. Retrieved June 10, 2019.
- "Local Calling Guide". Retrieved September 30, 2012.
|West: 970||Area code 303 / 720||East: 719|