| District of Colorado area codes: 303 | |
|---|---|
| Country | United States |
| State/Province | Colorado |
| Major City | Denver |
| Time Zone | Mountain (UTC-07:00) |
| Prefix | County | Primary City | Company |
|---|---|---|---|
| 303-343 | Arapahoe | Aurora, CO | Qwest Corporation |
| 303-344 | Arapahoe | Aurora, CO | Qwest Corporation |
| 303-345 | Denver | Denver, CO | Icg Telecom Group |
| 303-346 | Douglas | Littleton, CO | Qwest Corporation |
| 303-347 | Jefferson | Denver, CO | Qwest Corporation |
| 303-348 | Adams | Aurora, CO | Qwest Corporation |
| 303-349 | Jefferson | Denver, CO | Cellco Partnership DBA Verizon Wireless |
| 303-350 | Denver | Denver, CO | New Cingular Wireless PCS |
| 303-351 | Weld | Keenesburg, CO | 360networks (usa) Inc. |
| 303-352 | Denver | Denver, CO | Qwest Corporation |
| 303-353 | Denver | Denver, CO | Comcast Phone Of Colorado |
| 303-354 | Denver | Denver, CO | Teleport Communications America |
| 303-355 | Denver | Denver, CO | Qwest Corporation |
| 303-356 | Jefferson | Denver, CO | Sprint Spectrum L.p. |
| 303-357 | Denver | Denver, CO | Mcimetro Access Transmission Services LLC |
| 303-358 | Jefferson | Denver, CO | Cellco Partnership DBA Verizon Wireless |
| 303-359 | Jefferson | Denver, CO | T-mobile Usa |
| 303-360 | Arapahoe | Aurora, CO | Qwest Corporation |
| 303-361 | Arapahoe | Aurora, CO | Qwest Corporation |
| 303-362 | Arapahoe | Denver, CO | Teleport Communications America |
There are 783 prefixes, In the code area, the major cities are Arvada, CO;Aurora, CO;Boulder, CO;Brighton, CO;Bro. The major city is Denver.