image:Area code 410.svg, alt=area codes 227, 240, and 301. These numbers are related to the main zip codes of Maryland.,

Maryland Maryland ( ) is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic region of the United States. It borders the states of Virginia to its south, West Virginia to its west, Pennsylvania to its north, and Delaware to its east ...

's area codes highlighted in red and blue poly 336 37 323 30 310 13 305 -2 337 2

Area codes 215, 267, and 445 Area codes 215, 267, and 445 are telephone area codes in the North American Numbering Plan (NANP) for Philadelphia and adjacent portions of Bucks and Montgomery counties in the U.S. state of Pennsylvania. Area code 215 was one of the original ...

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Area code 856 Area code 856 is a telephone area code in the North American Numbering Plan (NANP) for the southwestern part of the U.S. state of New Jersey. The numbering plan area (NPA) includes the Camden, Cherry Hill, and Vineland areas and a small part of ...

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Area code 724 Area code 724 is a telephone area code in the North American Numbering Plan for the Commonwealth of Pennsylvania in western and southwestern Pennsylvania, including a portion of the suburbs of Pittsburgh. It was created in an area code split of ...

poly 181 143 184 134 195 144 186 156 184 147 182 142 Area code 202 poly 168 182 169 171 177 170 176 165 184 162 184 152 179 139 168 135 171 131 148 123 141 129 148 166 Area code 571 poly 327 230 290 235 282 236 283 246 317 243

Area codes 757 and 948 Image:Area code 757.png, The area colored red indicates the southeast corner of Virginia served by area code 757 poly 60 2 11 58 12 78 32 106 40 109 45 105 68 123 73 119 95 128 97 122 126 124 132 110 127 103 139 79 154 79 176 42 197 41 217 1 250 ...

poly 336 153 335 186 288 188 277 69 286 56 294 55 303 57 298 76 299 88 316 129

Area code 302 Area is the measure of a region's size on a surface. The area of a plane region or ''plane area'' refers to the area of a shape or planar lamina, while '' surface area'' refers to the area of an open surface or the boundary of a three-di ...

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Area codes 410, 443, and 667 image:Area code 410.svg, alt=area codes 227, 240, and 301. These numbers are related to the main zip codes of Maryland., Maryland's area codes highlighted in red and blue poly 336 37 323 30 310 13 305 -2 337 2 Area codes 215, 267, and 445 poly 3 ...

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Area code 804 Image:Area code 804.png, The area colored red indicates the geographical region of Virginia served by area code 804 poly 64 0 54 9 40 24 28 57 13 58 12 77 31 106 40 109 48 106 68 123 75 117 96 127 99 121 126 122 134 110 126 103 137 78 156 78 177 ...

poly 48 250 34 235 60 212 84 208 79 192 77 189 93 172 106 185 122 223 106 243 107 247

Area code 434 Image:Area code 434.png, The area colored red indicates the geographical region of Virginia served by area code 434 poly 64 0 54 9 40 24 28 57 13 58 12 77 31 106 40 109 48 106 68 123 75 117 96 127 99 121 126 122 134 110 126 103 137 78 156 78 17 ...

# poly 1 248 1 184 15 193 22 187 39 151 49 159 58 142 62 147 67 137 69 140 84 118 88 102 87 90 126 123 135 105 138 107 144 105 149 110 153 112 154 114 147 120 149 123 142 131 148 168 167 182 164 189 169 199 179 199 185 193 189 198 183 211 168 211 143 227 121 224 106 184 94 172 78 189 85 208 61 211 34 237 44 247 Area code 540 # desc bottom-left Area codes 410, 443, and 667 are telephone

area code A telephone numbering plan is a type of numbering scheme used in telecommunication to assign telephone numbers to subscriber telephones or other telephony endpoints. Telephone numbers are the addresses of participants in a telephone network, rea ...

s in the

North American Numbering Plan The North American Numbering Plan (NANP) is an integrated telephone numbering plan for twenty-five regions in twenty countries, primarily in North America and the Caribbean. This group is historically known as World Zone 1, World Numbering Zone ...

(NANP) for the eastern half of the

U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its so ...

. The numbering plan area (NPA) includes the

Baltimore metropolitan area The Baltimore–Columbia–Towson Metropolitan Statistical Area, also known as Central Maryland, is a metropolitan statistical area (MSA) in Maryland as defined by the United States Office of Management and Budget (OMB). It is part of the larger ...

and the Eastern Shore. The three area codes are overlay codes for one numbering plan area, among which 410 was the initial area code for the NPA, when it was

split Split(s) or The Split may refer to: Places * Split, Croatia, the largest coastal city in Croatia * Split Island, Canada, an island in the Hudson Bay * Split Island, Falkland Islands * Split Island, Fiji, better known as Hạfliua Arts, enter ...

from area code 301 in 1991. 443 and 667 found assignment primarily in cellular service and for competitive local exchange carriers, such as

Comcast Comcast Corporation, formerly known as Comcast Holdings,Before the AT&T Broadband, AT&T merger in 2001, the parent company was Comcast Holdings Corporation. Comcast Holdings Corporation now refers to a subsidiary of Comcast Corporation, not th ...

and Cavalier Telephone, when introduced, but have since become universal in carrier availability.

History

In 1947, the

American Telephone and Telegraph Company AT&T Corporation, an abbreviation for its former name, the American Telephone and Telegraph Company, was an American telecommunications company that provided voice, video, data, and Internet telecommunications and professional services to busi ...

(AT&T) published the first configuration of a nationwide

telephone numbering plan A telephone numbering plan is a type of numbering scheme used in telecommunication to assign telephone numbers to subscriber telephones or other telephony endpoints. Telephone numbers are the addresses of participants in a telephone network, reach ...

for Operator Toll Dialing, which designated the state of Maryland as a numbering plan area and assigned area code 301. Despite the state being home to two large metropolitan areas, Baltimore and the Maryland suburbs of

Washington, D.C. Washington, D.C., formally the District of Columbia and commonly known as Washington or D.C., is the capital city and federal district of the United States. The city is on the Potomac River, across from Virginia, and shares land borders with ...

( area code 202), the state received only one area code. This made Maryland one of the most-populous states to be served by a single area code. By the late 1980s, the rapid growth of the Baltimore and Washington suburbs, as well as the proliferation of

fax machine Fax (short for facsimile), sometimes called telecopying or telefax (short for telefacsimile), is the telephonic transmission of scanned printed material (both text and images), normally to a telephone number connected to a printer or other out ...

s and

pager A pager, also known as a beeper or bleeper, is a Wireless communication, wireless telecommunications device that receives and displays Alphanumericals, alphanumeric or voice messages. One-way pagers can only receive messages, while response p ...

s placed the numbering resources in the danger of exhaustion of central office prefixes. The number shortage problem was exacerbated by the use of area code 202 as a de facto overlay for the inner ring of the Washington metro area, even though it was split between three area codes–301, 202, and

Northern Virginia Northern Virginia, locally referred to as NOVA or NoVA, comprises several County (United States), counties and independent city (United States), independent cities in the Commonwealth (U.S. state), Commonwealth of Virginia in the United States. ...

's 703. This was accomplished via a system of central office code protection in which no central office code was duplicated in multiple area codes in the region. Each existing central office code was routed with each area code in the region so that each telephone number in the region could be dialed with any of the regional area codes. The consequence was that the full capacity of central office prefixes could not be used for each involved area code. The office code protection ended in 1990, but it soon became apparent that this would not free up enough prefixes to meet demand. By the fall of 1990, it was apparent that Maryland needed another area code. In November 1990, a plan for a second area code, 410, was announced, that would be assigned to the Baltimore metropolitan area and the Eastern Shore, while western and southern Maryland, including the Washington suburbs, would retain area code 301. Bell Atlantic (now

Verizon Verizon Communications Inc. ( ), is an American telecommunications company headquartered in New York City. It is the world's second-largest telecommunications company by revenue and its mobile network is the largest wireless carrier in the ...

), the largest telephone provider in the region, allowed the western part of the state to retain 301 to keep the large number of federal agencies on the Maryland side of the Washington area from having to change telephone numbers. On the other side of the

Potomac River The Potomac River () is in the Mid-Atlantic (United States), Mid-Atlantic region of the United States and flows from the Potomac Highlands in West Virginia to Chesapeake Bay in Maryland. It is long,U.S. Geological Survey. National Hydrography D ...

, many of the same factors resulted in most of the old 703 territory outside of Northern Virginia split off as area code 540 in 1995. While Maryland would have needed a second area code at some point due to rapid growth in the Washington and Baltimore suburbs, it is very likely that the immediate need for another area code would have been staved off had it been possible to assign more 301 numbers to the Baltimore area before 1990. Area code 410 officially entered service on October 6, 1991; it was initially implemented in a permissive-dialing phase, with

ten-digit dialing Ten-digit dialing is a telephone dialing procedure in the countries and territories of the North American Numbering Plan (NANP). It is the practice of including the area code of a telephone number when Dialling (telephony), dialing to initiate a t ...

for local calls across the new 301/410 boundary. The split largely followed metro lines. However, slivers of Anne Arundel and Carroll counties, as well as much of western Howard County, stayed in 301 even though these counties reckoned as part of the Baltimore area. Conversely, slivers of Frederick County, a Washington exurb, switched to 410."New area code for eastern Maryland". ''The Baltimore Sun''. November 1, 1991. p. 1A. Effective November 1, 1991,

was required when calling a different area code in Maryland. Although the split was intended to be a long-term solution, within five years 410 was already close to exhaustion due to the proliferation of

cell phones A mobile phone or cell phone is a portable telephone that allows users to make and receive Telephone call, calls over a radio frequency link while moving within a designated telephone service area, unlike fixed-location phones (landline phone ...

and pagers, particularly in and around Baltimore. To solve this problem, area code 443 was overlaid onto the 410 territory on July 1, 1997. Overlays were a new concept at the time, and had met resistance because of the requirement for

. However, the alternative would have been a split that would have forced residents of either Baltimore or the Eastern Shore to change their numbers for the second time in a decade. By 2011, the 410/443 area was once again running out of numbers because of the continued proliferation of cell phones. To spare residents another number change to a new area code, a third overlay code, area code 667, was implemented on March 24, 2012. This had the effect of assigning 24 million numbers to just over four million people. Based on current projections, a fourth area code will not be required in the region until about 2030.

Coverage

The counties served by these area codes include: In the Baltimore metropolitan area: * All of

Baltimore Baltimore is the most populous city in the U.S. state of Maryland. With a population of 585,708 at the 2020 census and estimated at 568,271 in 2024, it is the 30th-most populous U.S. city. The Baltimore metropolitan area is the 20th-large ...

and

, Calvert and Harford counties * Most of Anne Arundel, Carroll and

Howard Howard is a masculine given name derived from the English surname Howard. ''The Oxford Dictionary of English Christian Names'' notes that "the use of this surname as a christian name is quite recent and there seems to be no particular reason for ...

counties * A small portion of eastern Frederick County All of Maryland's Eastern Shore: * Caroline County * Cecil County * Dorchester County * Kent County * Queen Anne's County * Somerset County * Talbot County * Wicomico County * Worcester County

Explanatory notes

References

External links

List of cities covered and exchanges from Area-Codes.com, 410 Area Code

List of cities covered and exchanges from Area-Codes.com, 443 Area Code
{{Area code box, State=MD , This=410/443/667 , N= 717/223, 484/610/835 , S= 757/948 , E= 302,

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

, W= 301/240/227 , S1=DE , S2=PA , S3=VA 410 410 Communications in Baltimore Telecommunications-related introductions in 1991 Telecommunications-related introductions in 1997 Telecommunications-related introductions in 2012