Area Code Atlas

Split of NPA 301 and introduction of NPA 410 announced

Bellcore issued industry notification that Maryland's 301 numbering plan area would be split and that the new 410 area code would be introduced for the eastern part of the state. The notice established an effective split date of October 6, 1991 and described a permissive dialing period extending until November 1, 1992. It also documented the post-split geography, with 301 continuing to serve western and Washington-suburban Maryland.

NPA 410 split from 301 in Maryland

Area code 410 was created on October 5, 1991, as a split from 301 to address number exhaustion in Maryland. The new code covered most of Maryland from the Baltimore area eastward, while 301 continued to serve the Washington metropolitan area.

NPA 410 split from 301

Area code 410 officially entered service on October 6, 1991, following a split from 301. The new code covered the Baltimore metropolitan area and Maryland's Eastern Shore, while 301 continued to serve western and southern Maryland.

NPA 410 split from 301 for Baltimore and Eastern Shore

On November 1, 1991, area code 410 was created as a geographic split from area code 301. The new code served Baltimore, the Eastern Shore, and parts of central Maryland, while 301 continued to serve western Maryland and the Washington, D.C. suburbs.

Ten-digit dialing required for inter-NPA calls in Maryland

Effective November 1, 1991, ten-digit dialing became mandatory for calls between different area codes within Maryland, following the introduction of area code 410 and the split from 301.

NANP-Overlay of 410 (Maryland) Numbering Plan Area (NPA)

NPA 443 overlays 410

Area code 443 was overlaid onto the 410 territory on July 1, 1997, due to rapid number exhaustion in the Baltimore and Eastern Shore regions. This overlay introduced ten-digit dialing for all local calls within the region.

NPA 667 to Overlay NPAs 410 and 443 (Maryland)

Rationing in NPAs 410, 443, and 667 (Maryland)

NPA Code 667 to Overlay NPA Code 410/443 (Maryland)

NPA 667 implemented as a third overlay for 410/443

Area code 667 was implemented on March 24, 2012, as a third overlay for the 410 and 443 region in eastern Maryland. The addition of 667 provided relief for number exhaustion in the Baltimore metropolitan area and Maryland's Eastern Shore, addressing the continued demand for new numbers in the region.

Projected need for a fourth area code in the 410/443/667 region

Based on projections as of 2022, a fourth area code is expected to be required in the 410/443/667 region by about 2030 due to continued growth and number exhaustion.