510
Area code
CA
United States geographic area code, in service since 1991-09-02. Part of the 341/510 overlay complex — ten-digit dialing required.
Split from 415. Created 925. Created 341. Overlaid with 341 .
Statusin service
Introduced1991-09-02
JurisdictionCA, US
Local dialing1+10D
Time zonePacific
Last verified2026-09-17
Utilization 101% of assignable prefixes assigned
As of 09/17/2026
0%800 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 2001-01-25, most recent 2026-02-25.
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 | PACIFIC BELL | 278 | 34.8% |
| 02 | NEW CINGULAR WIRELESS PCS, LLC | 78 | 9.8% |
| 03 | T-MOBILE USA, INC. | 65 | 8.1% |
| 04 | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - CA | 60 | 7.5% |
| 05 | METROPCS, INC. | 45 | 5.6% |
| 06 | ONVOY, LLC - CA | 37 | 4.6% |
| 07 | MCIMETRO ACCESS TRANSMISSION SERVICES LLC | 37 | 4.6% |
| 08 | LEVEL 3 COMMUNICATIONS, LLC - CA | 34 | 4.3% |
| 09 | BANDWIDTH.COM CLEC, LLC - CA | 29 | 3.6% |
| 10 | TELEPORT COMMUNICATIONS AMERICA, LLC - CA | 19 | 2.4% |
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- 2010-11-22 NPA 510 (California) - Relief Plan Dismissed other
- 1991-09-02Area code 510 entered service (created from 415).
Planning letters & orders
Primary documents| Date | Document | Subject |
|---|---|---|
| 2018-07-30 | PL-518 ↗ | NPA 341 to Overlay 510 (California) |
| 2010-11-22 | PL-413 ↗ | NPA 510 (California) - Relief Plan Dismissed |
| 2000-01-14 | PL-206 ↗ | Overlays Suspended in the 408, 415, 510, 650, 714 & 909 NPAs |
| 1999-08-26 | PL-190 ↗ | NANP- Overlay of 510 Numbering Plan Area (NPA) with 341 NPA - California |
| 1990-06-13 | IL-90-06-023 ↗ | NANP - REVISED DATE FOR SPLIT OF 415 (CALIFORNIA) NUMBERING PLAN AREA |