North American Numbers Source-cited · ownership disclosed
Area code
443
In service
United States · since 1997

Baltimore (overlay)

An overlay of 410 covering the same eastern-Maryland territory (Baltimore metro and the Eastern Shore). It was the first overlay added to the 410 region, in service July 1, 1997.

The essentials Numbering data · NumberResearch · as of 2026-09-18
Place
Baltimore (overlay)
Type
geographic
Status
in service
In service since
1997
Projected exhaust
2036 Q1

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 443 is

Eastern Maryland: same footprint as 410 — Baltimore metro plus the nine Eastern Shore counties..

Communities served wholly or partly by 443:

BaltimoreAnnapolisTowsonColumbiaSalisburyBel AirOcean City

Same geography as 410 and 667 — an overlay, not a distinct area.

B · Relationships

How it relates to other codes

The codes 443 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?

Overlay · 1997 410 Baltimore 443 overlays 410; both share the eastern-Maryland footprint.
Overlay · 2012 667 Baltimore (overlay) Third code added to the same 410/443 region.
Related · 1991 301 Western/Southern Maryland (D.C. suburbs) 410 (443's base) originally split from 301.
What's changing. Overlay of 410 within the 410/443/667 complex; ten-digit dialing mandatory.
C · History

How 443 got here

1997-07-01
Area code 443 entered service as the first overlay of 410; ten-digit dialing required.
Source: Wikipedia
2012-03-24
Area code 667 added as a further overlay of the shared 410/443 region.
Source: Wikipedia
D · Capacity

How full it is

Prefixes assigned
800
Prefixes available
0
Thousands-blocks assigned
5,369

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

Compare 443 with another code →
Sources
Wikipedia ↗
Area code 443
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.