Area codes 303 and 720 are telephone area codes serving the state of Colorado. They cover Denver, Boulder, Longmont, Aurora and other areas in central Colorado. Area code 303 is overlaid with area code 720, meaning that the same physical service area is served by both area codes (303 and 720) and that ten-digit dialing is required for all calls made within the service area.
Prior to March 5, 1988, all of Colorado was served by the 303 area code but as the population grew, an impending phone number shortage forced a split of the state's area codes. Area code 719 was split from 303 on March 5, 1988, and 970 was split from the remaining 303 area on April 2, 1995, leaving 303 to cover its current area. 303 was overlaid with 720 on June 1, 1998.
With one exception (the Roggen area, which has local calling only with itself, Brighton, and Wiggins[1]), the entire 303/720 area is a local calling zone, so long distance is not applied to any calls made from one phone to another within the area.
With the exception mentioned above, all users in the 303/720 area code must dial all ten digits to reach a destination phone, even if that phone is next door. Some users in the area have shortened the two area codes to a single digit with a slash for easy writing. So 303-555-1212 is written down as 3/555-1212. Since 303 is the dominant (and older) area code, if a number appears without an area code it is generally assumed to be 303.
| Colorado area codes: 303, 719, 720, 970 | ||
|---|---|---|
| North: 970 | ||
| West: 970 | Area code 303 / 720 | East: 719 |
| South: 719 | ||