| 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 |
|---|---|---|---|
| 303-323 | Denver | Denver, CO | Mcimetro Access Transmission Services LLC |
| 303-324 | Jefferson | Denver, CO | New Cingular Wireless PCS |
| 303-325 | Denver | Denver, CO | Icg Telecom Group |
| 303-326 | Arapahoe | Aurora, CO | Qwest Corporation |
| 303-327 | Denver | Denver, CO | Icg Telecom Group |
| 303-328 | Denver | Denver, CO | Mcimetro Access Transmission Services LLC |
| 303-329 | Denver | Denver, CO | Qwest Corporation |
| 303-330 | Jefferson | Denver, CO | 360networks (usa) Inc. |
| 303-331 | Denver | Denver, CO | Qwest Corporation |
| 303-332 | Jefferson | Denver, CO | T-mobile Usa |
| 303-333 | Denver | Denver, CO | Qwest Corporation |
| 303-334 | Denver | Denver, CO | Mcimetro Access Transmission Services LLC |
| 303-335 | Denver | Denver, CO | Cellco Partnership DBA Verizon Wireless |
| 303-336 | Denver | Denver, CO | Qwest Corporation |
| 303-337 | Arapahoe | Aurora, CO | Qwest Corporation |
| 303-338 | Arapahoe | Aurora, CO | Qwest Corporation |
| 303-339 | Jefferson | Denver, CO | Cbeyond Communications |
| 303-340 | Arapahoe | Aurora, CO | Qwest Corporation |
| 303-341 | Arapahoe | Aurora, CO | Qwest Corporation |
| 303-342 | Adams | Aurora, CO | Qwest Corporation |
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.