Maryland Area Codes

Area codes: 6
ZIP codes: 605
Cities & towns: 431
Counties and independent cities: 24

Every area code in Maryland

All Maryland area codes, what each primarily serves, and which share ground with another.
Area code	Primarily serves	Shares ground with	In service
227	Baltimore	240, 301	2023
240	Baltimore	227, 301	1997
301	Baltimore	227, 240	1947
410	Baltimore	443, 667	1991
443	Baltimore	410, 667	1997
667	Baltimore	410, 443	2012

A code in the “shares ground” column is an overlay: it covers the same territory rather than a different part of Maryland, which is why local calls there are dialled as ten digits.

Which codes share the same ground

Maryland has 2 groups of codes that overlay one another: the codes inside a group cover the same territory rather than different parts of the state, so local calls there are dialled as ten digits.

227 240 301
410 443 667

Where Maryland's communities sit

Each point is a Maryland community, plotted from its record coordinates. The outline is the convex envelope of those points — a footprint, not a boundary.

Reference points and footprint
Not an official NANPA boundary
Not a USPS delivery area

Largest Maryland cities and their codes

largest 25

Scope every area code assigned to Maryland. Source LocalCallingGuide NPA list (2026-07 NPA list) and geoinfo-dataset (full_dataset) ZIP→NPA (2018 snapshot). Updated 16 July 2026. Overlay relationships come from the numbering-plan authority; the city match is computed.