Maryland area codes — detailed data

NANPA NPA database, current as of July 28, 2026.

Working detail for Maryland's 6 area codes: history, capacity forecasts and dialing plans, straight from NANPA's NPA database.

Aggregate footprint: the state's 6 geographic codes currently carry 3,691 active NXX prefixes over 449 rate-center anchorings, with 2,756 prefixes in thousands-block pooling. 6 of the codes serve territory inside FCC top-100 metropolitan statistical areas.

Lineage: 227 came out of 301 in 2023; 240 came out of 301 in 1997; 410 came out of 301 in 1991; 443 came out of 410 in 1997; 667 came out of 443 in 2012. The remaining code (301) dates back to the plan's early assignments.

Dialing plans: 6 codes use plain ten-digit local dialing (10D). Overlay territories always dial ten digits; the 2021 988-hotline transition moved most others to ten digits as well.

The tightest capacity in the state is 410 (complex 410/443/667), projected to exhaust 1Q 2036.

Status: no Maryland code is currently in jeopardy or active relief planning — capacity is adequate near-term per NANPA.

Code-by-code notes

240 — carved from 301; overlaid by 227/301; exhaust forecast 1Q 2041.

443 — spawned 667; carved from 410; overlaid by 410/667; exhaust forecast 1Q 2036.

301 — spawned 410, 240, 227; overlaid by 240/227; exhaust forecast 1Q 2041.

410 — spawned 443; carved from 301; overlaid by 443/667; exhaust forecast 1Q 2036.

667 — carved from 443; overlaid by 410/443; exhaust forecast 1Q 2036.

227 — carved from 301; overlaid by 240/301; exhaust forecast 1Q 2041.