Area codes 240 and 301
North American area codes 240 and 301 are telephone area codes for the western half of Maryland. They serve Maryland's portion of the Greater Washington, D.C. metro area, portions of southern Maryland, and all points northwest of Washington. This includes the communities of Cumberland, Frederick, Hagerstown, Gaithersburg, Rockville, Landover and Silver Spring, Maryland.
The main area code, 301, was one of the original area codes established in 1947. It originally served the entire state, even though it is home to two very large metropolitan areas, Baltimore and the suburbs of Washington, D.C. The North American Numbering Plan Administrator wanted to keep the number of "clicks" to a minimum for densely populated areas given the rotary dialing technology in use at the time. Codes with as few as five clicks were possible for area codes covering just a city or portion of a state under NANPA's original guidelines (0 and 1 were not allowed as the first digit, the second digit was either 0 or 1, and the third digit could not be the same as the second digit). However, area codes covering an entire state always had 0 as the middle digit, for a minimum of 13 clicks. Taking Maryland's density into account, NANPA assigned it an area code with 14 clicks (3+10+1), tied with the District's 202 as the second-fastest single-state area code that could be dialed under NANPA's original guidelines (behind New Jersey's 201).
From 1947 to 1991, it was possible for telephone users on the Maryland side of the Washington metropolitan area to dial any number in the region with only seven digits. This was possible because the Maryland side of the metro shares an LATA with Northern Virginia--which is in area code 703--and the District itself. Every number on the Maryland and Virginia sides of the metro was also given a "hidden" number in the District's area code 202, essentially making 202 an overlay for the entire metro. One consequence of this was that no prefixes could be duplicated in the three area codes. For instance, if 202-57x was in use in the District, the corresponding 301-57x exchange could not be used anywhere in Maryland, even in areas a safe distance from the Washington metro area such as the Eastern Shore. By the end of the 1980s, exchanges on both sides of the Potomac River were running out of numbers. To free up available numbers, the partial overlay with 202 was ended in 1991.
Despite the presence of the Baltimore-Washington 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, the Baltimore-Washington corridor's rapid growth made it obvious that Maryland needed a second area code. The supply of numbers was further limited by the single-LATA status of the Washington area, meaning several numbers in 703 and 202 weren't available for use. Finally, Baltimore and the Eastern Shore were split off as area code 410 on October 6, 1991. The split largely followed metro area lines. However, part of Howard County, which is reckoned as part of the Baltimore area, stayed in 301 while the rest shifted to 410.
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, the overlay area code 240 was introduced on June 1, 1997. Overlays were a new concept at the time, and met with some resistance due to the requirement for ten-digit dialing. However, Bell Atlantic, the state's dominant carrier, wanted to spare residents the burden of having to change their numbers.
Area code 227 is scheduled to be overlaid with 301/240 some time in the longer term to provide additional assignable numbers, although the current area codes are not expected to exhaust before 2020.
Counties served by these area codes include:
- Howard (shared with 410/443/667)
- Prince George's
- St. Mary's
- A very small portion of southwestern Carroll County
Local calls require 10-digit dialing (area code + number, leading "1" is not required).
- 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: 717, 724/878, 814|
|West: 202, 304/681, 540, 571/703||area codes 301/240||East: 410/443/667|
|South: 804, 304/681|
|District of Columbia area codes: 202|
|Pennsylvania area codes: 215, 267, 412, 484, 570, 610, 717, 724, 814, 878|
|Virginia area codes: 276, 434, 540, 571, 703, 757, 804|
|West Virginia area codes: 304/681|