North American Numbers Source-cited · ownership disclosed
Area code
410
In service
United States · since 1991

Baltimore

Serves eastern Maryland, including the Baltimore metropolitan area and the entire Eastern Shore. It split from 301 in 1991 and is now the base code of the 410/443/667 overlay complex.

The essentials Numbering data · NumberResearch · as of 2026-09-18
Place
Baltimore
Type
geographic
Status
in service
In service since
1991
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 410 is

Eastern Maryland: Baltimore City and Baltimore County, Anne Arundel, Carroll, Harford, Howard, Calvert, a small part of Frederick, and all nine Eastern Shore counties..

Communities served wholly or partly by 410:

BaltimoreAnnapolisTowsonColumbiaSalisburyBel AirOcean City

Overlay complex — 410, 443, and 667 all serve the same territory; ten-digit dialing required.

B · Relationships

How it relates to other codes

The codes 410 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?

Split from · 1991 301 Western/Southern Maryland (D.C. suburbs) Split off from 301 in 1991 to relieve statewide exhaustion.
Overlay · 1997 443 Baltimore (overlay) First overlay of 410, in service July 1, 1997.
Overlay · 2012 667 Baltimore (overlay) Second overlay of 410/443, in service March 24, 2012.
Related · 1997 240 Western/Southern Maryland (overlay) Serves the adjacent western-Maryland 301 region.
Related · 2023 227 Western/Southern Maryland (overlay) Serves the adjacent western-Maryland 301 region.
What's changing. Base code of the 410/443/667 all-services overlay complex covering eastern Maryland; ten-digit dialing mandatory.
C · History

How 410 got here

1947
Maryland assigned the single original area code 301 (301 covered the whole state).
Source: Wikipedia
1991-10-06
Area code 410 entered service, split from 301, serving Baltimore and the Eastern Shore.
Source: Wikipedia
1997-07-01
Area code 443 overlaid onto 410 territory — Maryland pioneered overlays rather than further splits.
Source: Wikipedia
2012-03-24
Area code 667 added as a second overlay of the 410/443 region.
Source: Wikipedia
D · Capacity

How full it is

Prefixes assigned
800
Prefixes available
0
Thousands-blocks assigned
1,885

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

Compare 410 with another code →
Sources
Wikipedia ↗
Area code 410
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.