North American Numbers Source-cited · ownership disclosed
Area code
203
In service
United States · since 1947

Southwestern Connecticut

One of the original 1947 area codes, 203 originally covered all of Connecticut before the 1995 split reduced it to the southwestern part of the state. It is now overlaid by 475.

The essentials Numbering data · NumberResearch · as of 2026-09-18
Place
Southwestern Connecticut
Type
geographic
Status
in service
In service since
1947
Projected exhaust
2055 Q4

Status, dates and counts are read from NumberResearch (NANPA / CNAC / FCC records). Assignment records show initial assignees, not the carrier serving a number today.

A · Where it is

Where 203 is

Southwestern Connecticut, largely the Connecticut portion of the New York metropolitan area. Most of Fairfield County, all of New Haven County, and parts of Litchfield County..

Communities served wholly or partly by 203:

BridgeportNew HavenWaterburyStamfordNorwalkDanburyMeriden

Serves 50+ municipalities in total.

B · Relationships

How it relates to other codes

The codes 203 was split from, spawned, or shares its area with. A split divides the map and changes some numbers; an overlay shares the same ground and changes none — what's the difference?

Spawned · 1995 860 Connecticut (except southwest) On August 28, 1995 Connecticut was divided; 860 was created for the rest of the state while 203 was reduced to the southwest.
Overlay · 2009 475 Southwestern Connecticut (overlay) 475 overlays the same 203 geographic area, in service December 12, 2009.
Related · 2014 959 Connecticut except southwest (overlay) Overlay of adjacent 860; not the same territory as 203.
What's changing. Overlaid by 475 since December 12, 2009; ten-digit dialing required.
C · History

How 203 got here

1947
Area code 203 established as one of the original 86 North American area codes, covering all of Connecticut.
Source: Wikipedia
1995-08-28
Connecticut split; 203 reduced to the southwestern region and 860 assigned to the remainder of the state.
Source: Wikipedia
2009-12-12
Area code 475 added as an overlay of 203.
Source: Wikipedia
D · Capacity

How full it is

Prefixes assigned
800
Prefixes available
0
Thousands-blocks assigned
2,755

Prefix-assignment counts describe allocation to carriers, not how many individual numbers are in use. Full technical records: NumberResearch ↗.

Compare 203 with another code →
Sources
Wikipedia ↗
Area code 203
NumberResearch.org ↗
Live status, dates, assignment counts and exhaust forecast — data as of 2026-09-18 (CC BY 4.0).

Place, relationships and history above are compiled by North American Numbers from the sources listed and last checked 2026-09-18. A check date is not an expert review — see how this is made. Flag an error.