557
Area code
MO
United States geographic area code, in service since 2022-08-12. Part of the 314/557 overlay complex — ten-digit dialing required.
Statusin service
Introduced2022-08-12
JurisdictionMO, US
Local dialing10D
Time zoneCentral
Last verified2026-09-17
Utilization 12% of assignable prefixes assigned
As of 09/17/2026
0%95 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 2022-08-08, most recent 2026-09-09.
Area codes serve rate-center geographies, not municipal boundaries. “MO” identifies the jurisdiction, not an exact city footprint.
Top assignees
Ranked by assigned prefixes · initial assignee ≠ current carrier| Rank | Assignee | Prefixes | Share |
|---|---|---|---|
| 01 | NEW CINGULAR WIRELESS PCS, LLC - IL | 23 | 24.2% |
| 02 | ONVOY, LLC - MO | 17 | 17.9% |
| 03 | TELEPORT COMMUNICATIONS AMERICA, LLC - MO | 15 | 15.8% |
| 04 | MULTIPLE OCN LISTING | 9 | 9.5% |
| 05 | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MO | 8 | 8.4% |
| 06 | 5 | 5.3% | |
| 07 | ONVOY SPECTRUM, LLC | 3 | 3.2% |
| 08 | TERRA NOVA TELECOM INC. | 2 | 2.1% |
| 09 | T-MOBILE USA, INC. | 2 | 2.1% |
| 10 | FIVE9, INC. | 2 | 2.1% |
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- 2021-10-28 NPA 557 to Overlay NPA 314 (Missouri)
- 2022-08-12Area code 557 entered service (created from 314).
Planning letters & orders
Primary documents| Date | Document | Subject |
|---|---|---|
| 2021-10-28 | PL-567 ↗ | NPA 557 to Overlay NPA 314 (Missouri) |
| 2001-10-05 | PL-303 ↗ | Suspension of the 314 NPA Relief (Missouri) |
| 2001-05-09 | PL-279 ↗ | NPA 557 Overlay of NPA 314 Implementation Date and Dialing Plan Change (Missouri) |
| 2001-02-14 | PL-261 ↗ | New NPA 557 to Overlay NPA 314 (Missouri) |