Area codes in Maryland

Maryland has 6 area codes, per NANPA’s NPA report of 2026-09-27. The NANPA central office code report of 2026-09-27 lists 3,729 allocated central office codes there across 165 rate centres, 74.9% of them pooled; 59 were assigned in the twelve months from 2025-09-28.

The area codes of Maryland

Each code with the place its page names, the year or day NANPA’s NPA report puts it in service, the codes it shares its area with, and the central office codes the NANPA central office code report allocates under it whose rate centre is in Maryland. A rate centre is where the regulator recorded a code, not where a subscriber is.

code	place	in service	overlays	codes here	assigned, 12 months
227	—	2023-06-14	240, 301	140	33
240	—	1997-06-01	227, 301	785	0
301	—	1947	227, 240	784	0
410	—	1991-10-06	443, 667	783	0
443	—	1997-06-01	410, 667	785	0
667	—	2012-03-24	410, 443	452	26

A year alone means NANPA’s date is 1 January of that year, which it uses where it records no day.

Overlays and new area codes

227, 240 and 301 serve one area: a number there can carry any of these 3 codes, so the area code alone does not place a number more precisely than the area.
410, 443 and 667 serve one area: a number there can carry any of these 3 codes, so the area code alone does not place a number more precisely than the area.

What the NANPA central office code report holds for Maryland

area codes	6
allocated codes	3,729 central office codes, 10,000 numbers each
rate centres	165
pooled codes	2,794 (74.9%)
codes assigned since 2025-09-28	59
thousands-blocks assigned since 2025-09-28	784

A pooled code is split into thousands-blocks of 1,000 numbers that other carriers may hold. The twelve months run to the table’s own date, so the figures change only when the table does.

Allocated codes by network brand

Each code is counted under the holder the NANPA central office code report lists for it, grouped under today’s network brand. That is the code’s original allocation, never who serves a number today, since numbers move between carriers, and the shares are shares of the regulator’s table, not of subscribers or traffic. In a pooled code the thousands-blocks can be held by other carriers; this counts the code’s holder.

brand	codes	share
Verizon	1,622	43.5%
AT&T	465	12.5%
T-Mobile	425	11.4%
Windstream	239	6.4%
Inteliquent	230	6.2%
Lumen	185	5.0%
Bandwidth	88	2.4%
Peerless Network	52	1.4%
Not under a listed brand (49 holders)	423	11.3%

Where these figures come from

The codes, rate centres, pooling and assignment dates are counted from the NANPA central office code report of 2026-09-27, and the area codes, overlays and in-service dates from NANPA’s NPA report of 2026-09-27. Counts only: no row of either file is republished here. The publisher, its files and its terms are on the data source page. Every area code of the United States is on the United States page, the codes put in service lately or still to come across North America on new and upcoming area codes, and any number can be read on the free phone number lookup.

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