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.
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.
This page was last updated on July 3, 2015.