Area Code 303 History:
Area code 303 was put into service. In 1988 Area code 303 was split to form area code 719. In 1995 area code 303 was split to form area code 970. In 1998 area code 303 was overlaid with area code 720.
Counties in Colorado within area code 303 include:
Adams County, Arapahoe County, Boulder County, Broomfield County, Clear Creek County, Denver County, Douglas County, Eagle County, El Paso County, Elbert County, Gilpin County, Jefferson County, Park County, Sedgwick County, and Weld County.
Major cities or places in Colorado within area code 303 include:
Area codes 303 and 720 serve central Colorado including the larger cities and communities of Aurora, Boulder, Brighton, Broomfield, Castle Rock, Castlewood, Columbine, Commerce City, Denver, Englewood, Highlands Ranch, Ken Caryl, Lafayette, Lakewood, Littleton, Longmont, Loveland, Northglenn, Parker, Southglenn, Thornton, Westminster and Wheat Ridge in addition to many smaller communities.