203
Area code
CT
United States geographic area code, in service since 1947-01-01. Part of the 203/475 overlay complex — ten-digit dialing required.
Statusin service
Introduced1947-01-01
JurisdictionCT, US
Local dialing10D
Time zoneEastern
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 2001-01-03, most recent 2024-09-18.
Area codes serve rate-center geographies, not municipal boundaries. “CT” identifies the jurisdiction, not an exact city footprint.
Top assignees
Ranked by assigned prefixes · initial assignee ≠ current carrier| Rank | Assignee | Prefixes | Share |
|---|---|---|---|
| 01 | SOUTHERN NEW ENGLAND TELCO DBA FRONTIER COMM OF CT | 338 | 42.3% |
| 02 | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - CT | 61 | 7.6% |
| 03 | NEW CINGULAR WIRELESS PCS, LLC - DC | 52 | 6.5% |
| 04 | OMNIPOINT COMMUNICATIONS, INC. - CT | 47 | 5.9% |
| 05 | LEVEL 3 COMMUNICATIONS, LLC - CT | 41 | 5.1% |
| 06 | PAETEC ITEL, LLC | 40 | 5% |
| 07 | MCIMETRO ACCESS TRANSMISSION SERVICES LLC - CT | 37 | 4.6% |
| 08 | TELEPORT COMMUNICATIONS AMERICA, LLC - CT | 33 | 4.1% |
| 09 | CABLEVISION LIGHTPATH, INC. - CT | 29 | 3.6% |
| 10 | METROPCS, INC. | 25 | 3.1% |
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- 2009-04-14 NPA 475 to Overlay NPA 203; NPA 860 10-digit dialing (Connecticut)
- 1947-01-01Area code 203 entered service.
Planning letters & orders
Primary documents| Date | Document | Subject |
|---|---|---|
| 2009-04-14 | PL-388 ↗ | NPA 475 to Overlay NPA 203; NPA 860 10-digit dialing (Connecticut) |
| 2001-01-03 | PL-255 ↗ | Update on the Introduction of NPAs 475 and 959 (Connecticut) |
| 2000-02-24 | PL-217 ↗ | NPA 475 To Overlay NPA 203; NPA 959 To Overlay NPA 860 (Connecticut) |
| 1998-10-05 | PL-138 ↗ | Extraordinary NPA-Specific Jeopardy Conservation Procedures Announced for Connecticut NPAs 203 & 860 |