Area codes 303 and 720
Area codes 303 and 720 are telephone area codes serving the north-central portion of the state of Colorado. They cover Denver, Lakewood, Littleton, Boulder, Longmont, Aurora, Castle Rock and most of the Front Range. Area code 303 is the main area code, while area code 720 is an overlay, 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.
Area code 303 was one of the original area codes put into service in 1947, and originally covered the entire state of Colorado. However, due to Colorado's explosive growth during the second half of the 20th century (particularly in the Denver area), an impending number shortage made a split necessary. On March 5, 1988, southeastern Colorado became area code 719. The northeastern and western portions of area code 303 switched to area code 970 on April 2, 1995, leaving area code 303 to cover its current area.
The 1995 split was intended as a long-term solution. However, within two years 303 was close to exhaustion once again. 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. To solve this problem, 720 was activated as an overlay on June 1, 1998.
With the exception of the Roggen area, which has local calling only with itself, Brighton and Wiggins, the entire 303/720 area is a local calling zone, meaning no long-distance charges are 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.
- "Local Calling Guide". Retrieved September 30, 2012.
|Colorado area codes: 303, 719, 720, 970|
|West: 970||Area code 303 / 720||East: 719|