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  5. Area Code 303

Where Is Area Code 303?

Area code 303 is found in the US state of Colorado. Primarily servicing the city of Denver (population: 622214), area code 303 covers 16 counties of Colorado.

Located in the Mountain time zone, area code 303 is on the same time as Phoenix, AZ.

Area code 303 was brought into effect on January 1, 1947.

Map of  with area code 303 highlighted

Counties in Area Code 303

  • Adams,
  • Arapahoe,
  • Boulder,
  • Broomfield,
  • Clear Creek,
  • Denver,
  • Douglas,
  • El Paso,
  • Elbert,
  • Gilpin,
  • Jefferson,
  • Larimer,
  • Park,
  • Weld.

Most Populous Cities in Area Code 303

City County City Population Time Zone
Denver Denver 622,214 MST
Aurora Arapahoe 403,275 MST
Denver Adams 197,953 MST
Denver Jefferson 170,239 MST
Littleton Jefferson 125,559 MST
Boulder Boulder 125,344 MST
Arvada Jefferson 124,718 MST
Longmont Boulder 121,868 MST
Littleton Douglas 108,591 MST
Englewood Arapahoe 103,715 MST
Parker Douglas 88,512 MST
Littleton Arapahoe 79,200 MST
Castle Rock Douglas 70,429 MST
Broomfield Broomfield 64,777 MST
Brighton Adams 64,003 MST
Golden Jefferson 58,763 MST
Westminster Adams 51,228 MST
Commerce City Adams 44,438 MST
Thornton Adams 33,039 MST
Louisville Boulder 32,166 MST
Broomfield Jefferson 30,718 MST
Lafayette Boulder 27,340 MST
Wheat Ridge Jefferson 24,453 MST
Evergreen Jefferson 24,159 MST
Erie Weld 21,069 MST

Note: The above list is based off of the top 25 most populous cities in the area code as per 2012 United States Census Bureau estimates.

View all United States Area Codes.

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This page was last updated on July 3, 2015.