North American area codes 301 and 240 are telephone area codes for the western part of Maryland. They serve Maryland's portion of the Greater Washington, D.C., metro area, portions of southern Maryland, and the more rural areas in the western portion of the state. This includes the communities of Cumberland, Frederick, Hagerstown, Gaithersburg, Rockville, Landover and Silver Spring.
From 1947 to 1990, the telephone numbering plan of the entire Washington metropolitan area, including Washington, D.C. (area code 202), and the large suburban areas in Maryland and Virginia (area code 703), operated in a system of central office code protection, meaning that no central office code in Washington D.C., and in the Maryland and Virginia suburbs could exist in more than a single central office. As a result, it was possible for telephone users in the Washington metropolitan area to dial any telephone number in the metro area with only seven digits, without using an area code, and without toll charges. Furthermore, the entire metro area was reachable via long distance services by using any of the three area codes, for which purpose AT&T had established cross-referenced operator routing codes for all affected central offices.
The Eastern Shore of Maryland was at a safe distance from Washington to permit use of central office codes in use in the D.C. and Virginia areas.
By the end of the 1980s, the Washington metropolitan area was running out of prefixes. This code exhaustion was mitigated on October 1, 1990, by removing code protection in 202. As of that date, all local metro area calls between Maryland, the District of Columbia, and Virginia required dialing an area code for call to another numbering plan area (NPA). Local calls within Maryland did not require the area code.
Despite the overall growth of the Baltimore–Washington metropolitan area, 301 remained the exclusive area code for Maryland for 44 years, making Maryland one of the largest states with a single area code. By the end of the 1980s, however, it became apparent that breaking seven-digit dialing in the Washington area would not free up enough numbers to stave off the need for a new area code.
Baltimore and the Eastern Shore were split off as a new numbering plan area with area code 410 on October 6, 1991. The split largely followed metro area lines. However, part of Howard County, which is recognized as part of the Baltimore area, stayed in 301, while the rest shifted to 410. Normally, when an area code is split, the largest city in the old numbering plan area retains the existing area code—in this case, Baltimore. However, it was decided to let the Washington suburbs keep 301. Not only do the Washington suburbs have the bulk of the state's population, but Bell Atlantic (now Verizon) wanted to spare the large number of federal agencies on the Maryland side of the metro the expense and burden of having to change their numbers.
This was intended as a long-term solution, but within four years 301 was close to exhaustion due to the proliferation of cell phones and pagers, especially in the Washington suburbs. To solve this problem, area code 240 was introduced on June 1, 1997, as the state's first overlay area code. Overlays were a new concept at the time, and met with some resistance due to the requirement for ten-digit dialing. For this reason, conventional wisdom would have suggested a split in which the Washington suburbs would have kept 301 while Frederick and points west would have shifted to 240. However, Bell Atlantic wanted to spare residents, particularly in the more rural western portion, the burden of having to change their numbers.
Area code 227 is scheduled to be overlaid on 301/240 some time in the longer term to provide additional assignable numbers, although the current area codes are not expected to exhaust before 2024.
The counties served by area codes 301 and 240 include Allegany, Charles, Frederick,[a] Garrett, Howard,[a] Montgomery, Prince George's, St. Mary's, Washington, and a very small portions of southwestern Carroll County[a] and western Anne Arundel County.[a]
Local calls require ten-digit dialing (area code + number, leading "1" is not required).
- Four counties were split between area code 301 and 410.
- Anne Arundel County was assigned area code 410, except Laurel exchanges 210, 317, 490, 497, 498, 596, 604, 725, and 778 and Marlboro exchange 952 remained area code 301.
- Carroll County was assigned area code 410, except Mount Airy exchange 829 remained area code 301.
- Howard County was assigned area code 410, except Mount Airy exchange 829 and Laurel exchanges 210, 317, 490, 497, 598, 604, 725, and 776 remained area code 301.
- Frederick County remained area code 301, except Union Bridge exchange 775 and New Windsor exchange 635 was assigned 410.
- AT&T Long Lines, Distance Dialing Reference Guide (April 1974)
- Jordan, Mary; Quimpo, Margie G. (September 23, 1990). "Territorial Telephones; On Oct. 1, Local Calls Will Get Complicated". The Washington Post. p. 1.
- "Bellcore Letter IL-90/12-049" (PDF). North American Numbering Plan Administration. Neustar. Retrieved June 21, 2013.
- "Bellcore Letter IL 96/06-009" (PDF). North American Numbering Plan Administration. Neustar. Retrieved 21 June 2013.
- "New area code for eastern Maryland". The Baltimore Sun. November 1, 1991. p. 1A.
- NANPA area code map of Maryland
- List of exchanges from AreaCodeDownload.com, 301 Area Code
- List of exchanges from AreaCodeDownload.com, 240 Area Code
|Maryland area codes: 240/301, 410/443/667|
|North: 223/717, 412/724/878, 814|
|West: 202, 304/681, 540, 571/703||area codes 240/301||East: 410/443/667|
|South: 804, 304/681|
|District of Columbia area codes: 202|
|Pennsylvania area codes: 215/267/445, 223/717, 272/570, 412, 484/610, 724, 814, 878|
|Virginia area codes: 276, 434, 540, 571/703, 757, 804|
|West Virginia area codes: 304/681|