CO
United States geographic area code, in service since 1947-01-01. Part of the 303/720/983 overlay complex — ten-digit dialing required.
Created 719. Created 970. Created 720. Created 983. Overlaid with 720, 983 .
Prefix-level assignment does not equal number-level exhaustion; thousands-block pooling extends capacity. First assignment on record 2001-04-12, most recent 2025-01-16.
Area codes serve rate-center geographies, not municipal boundaries. “CO” identifies the jurisdiction, not an exact city footprint.
Top assignees
Ranked by assigned prefixes · initial assignee ≠ current carrier| Rank | Assignee | Prefixes | Share |
|---|---|---|---|
| 01 | QWEST CORPORATION | 449 | 56.1% |
| 02 | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - CO | 60 | 7.5% |
| 03 | LEVEL 3 COMMUNICATIONS, LLC - CO | 58 | 7.2% |
| 04 | T-MOBILE USA, INC. | 39 | 4.9% |
| 05 | NEW CINGULAR WIRELESS PCS, LLC | 35 | 4.4% |
| 06 | SPOK, INC. | 31 | 3.9% |
| 07 | MCIMETRO ACCESS TRANSMISSION SERVICES LLC | 31 | 3.9% |
| 08 | TELEPORT COMMUNICATIONS AMERICA, LLC - CO | 28 | 3.5% |
| 09 | ONVOY, LLC - CO | 14 | 1.8% |
| 10 | AMERICAN MESSAGING SERVICES, LLC | 11 | 1.4% |
Important: these are initial assignees from NANPA CO-code records — the carrier a prefix was originally assigned to. Because of number portability, the current serving carrier of any individual number may differ.
Change history
Recorded events for this NPA- 2021-07-29 NPA 983 to Overlay NPA 303/720 (Colorado)
- 1997-07-14 Declaration of Jeopardy Situation in NPA 303 (Colorado) jeopardy
- 1947-01-01Area code 303 entered service.
Planning letters & orders
Primary documents| Date | Document | Subject |
|---|---|---|
| 2021-07-29 | PL-563 ↗ | NPA 983 to Overlay NPA 303/720 (Colorado) |