424
Area code
CA
United States geographic area code, in service since 2006-08-26. Part of the 310/424 overlay complex — ten-digit dialing required.
Statusin service
Introduced2006-08-26
JurisdictionCA, US
Local dialing1+10D
Time zonePacific
Last verified2026-09-17
Utilization 60% of assignable prefixes assigned
As of 09/17/2026
0%475 of ~792 assignable NXX values (200–999 excl. N11)100%
Prefix-level assignment does not equal number-level exhaustion; thousands-block pooling extends capacity. First assignment on record 2006-03-16, most recent 2026-09-03.
Area codes serve rate-center geographies, not municipal boundaries. “CA” identifies the jurisdiction, not an exact city footprint.
Top assignees
Ranked by assigned prefixes · initial assignee ≠ current carrier| Rank | Assignee | Prefixes | Share |
|---|---|---|---|
| 01 | T-MOBILE USA, INC. | 74 | 15.6% |
| 02 | ONVOY, LLC - CA | 69 | 14.5% |
| 03 | BANDWIDTH.COM CLEC, LLC - CA | 45 | 9.5% |
| 04 | LEVEL 3 COMMUNICATIONS, LLC - CA | 42 | 8.8% |
| 05 | NEW CINGULAR WIRELESS PCS, LLC | 36 | 7.6% |
| 06 | FRACTEL, LLC | 33 | 6.9% |
| 07 | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - CA | 30 | 6.3% |
| 08 | METROPCS NETWORKS, LLC | 23 | 4.8% |
| 09 | TELEPORT COMMUNICATIONS AMERICA, LLC - CA | 17 | 3.6% |
| 10 | ONVOY SPECTRUM, LLC | 12 | 2.5% |
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- 2005-09-07 NPA 424 to Overlay NPA 310 (California)
- 2006-08-26Area code 424 entered service (created from 310).
Planning letters & orders
Primary documents| Date | Document | Subject |
|---|---|---|
| 2005-09-07 | PL-347 ↗ | NPA 424 to Overlay NPA 310 (California) |
| 2000-11-10 | PL-250 ↗ | 310 NPA Splits, Creating 424 NPA (California) |
| 1998-05-26 | PL-125 ↗ | NANP-Overlay of 310 (California) Numbering Plan Area (NPA) with 424 NPA |