Area codes 303, 720, and 983 are telephonearea codes in theNorth American Numbering Plan (NANP) for the north-central portion of theU.S. state ofColorado. The numbering plan area (NPA) comprisesDenver andBoulder, as well as their surrounding suburbs, includingLakewood,Littleton,Longmont,Broomfield,Aurora, andCastle Rock. Area code 303 is the original area code of the NPA, as well as for the entire state, reduced in geographic extent over time. Area codes 720 and 983 were added in 1998 and 2022, respectively, to form anoverlay complex for the area, meaning that the same geographic service area is served by all area codes and thatten-digit dialing is required for all calls made within the service area.
Area code 303 was one of theoriginal North American area codes of 1947, and originally served the entire state of Colorado. It remained the state's sole area code for 40 years.
Colorado's explosive growth in the second half of the 20th century, particularly in the Denver/Boulder area, made it a certainty that Colorado would need another area code. An impending number shortage in the late 1980s meant this split could no longer be staved off. On March 5, 1988, southeastern Colorado, includingColorado Springs andPueblo, was split off asarea code 719.[2]
This was intended as a long-term solution, but within five years further demand for numbers and the proliferation of cell phones and pagers (especially in and around Denver) forced another split. The northeastern and western portions of area code 303, includingFort Collins,Grand Junction,Vail andAspen, were separated on April 2, 1995, and becamearea code 970. This split reduced 303 to the Denver-Boulder area.[3] With the 1995 split, 303 was the only Colorado area code that did not border another state.
Within two years, continued sharp growth in theFront Range made further relief 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 instituted in the 303 service area to create anoverlay.[4]
In 2020, the North American Numbering Plan Administrator estimated that the Denver metropolitan area would reach numbering exhaustion by 2023.[5] Accordingly, the Colorado Public Utilities Commission approved on May 21, 2021 an additional area code for the all-services distributed overlay of NPA 303/720.[6][7] Area code 983 was activated on June 17, 2022. No central office codes in 983 were allowed to be installed before complete exhaustion of the previous area codes.[6] This latest addition resulted in 23.8 million numbers being assigned to an area of about 3.5 million people.[8]
The numbering plan area is one of the largest toll-free calling zones in the western United States.[citation needed] With the exception ofRoggen,Brighton, andWiggins,[9][failed verification] no long-distance charges are levied for any calls made from one telephone to another in the area.
303 Day, named for the area code, is an unofficial holiday on which Colorado businesses celebrate their state by offering discounts on March 3. The observance was created in 2009 by Jeb Freedman, aKTCL radio personality, and members of the band3OH!3.[10]
| North:970 | ||
| West:970 | 303/720/983 | East:719 |
| South:719 |