| 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 |
|---|---|---|---|
| 303-383 | Denver | Denver, CO | Qwest Corporation |
| 303-384 | Jefferson | Golden, CO | Qwest Corporation |
| 303-385 | Denver | Denver, CO | Icg Telecom Group |
| 303-386 | Denver | Denver, CO | Icg Telecom Group |
| 303-387 | Denver | Denver, CO | Mcleodusa Telecommunications Services- Co |
| 303-388 | Denver | Denver, CO | Qwest Corporation |
| 303-389 | Denver | Denver, CO | Qwest Corporation |
| 303-390 | Denver | Denver, CO | Mcimetro Access Transmission Services LLC |
| 303-391 | Denver | Denver, CO | Qwest Corporation |
| 303-392 | Jefferson | Denver, CO | Contact Paging Of Colorado |
| 303-393 | Denver | Denver, CO | Qwest Corporation |
| 303-394 | Denver | Denver, CO | Qwest Corporation |
| 303-395 | Jefferson | Denver, CO | Global Crossing Local Services-co |
| 303-396 | Jefferson | Denver, CO | Live Wire Networks |
| 303-397 | Jefferson | Denver, CO | Qwest Corporation |
| 303-398 | Denver | Denver, CO | Qwest Corporation |
| 303-399 | Denver | Denver, CO | Qwest Corporation |
| 303-400 | Jefferson | Denver, CO | Qwest Corporation |
| 303-401 | Jefferson | Denver, CO | Qwest Corporation |
| 303-402 | Jefferson | Denver, 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.