Английская Википедия:Area codes 410, 443, and 667

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Шаблон:Short description Шаблон:More citations needed Шаблон:Use mdy dates <imagemap> image:Area code 410.svg|right|300px|thumb|alt=area codes 227, 240, and 301. These numbers are related to the main zip codes of Maryland.|Maryland consists of the red and blue areas. The blue area has area codes 227, 240 and 301. poly 336 37 323 30 310 13 305 -2 337 2 Area codes 215, 267, and 445 poly 339 121 325 118 296 86 296 73 307 56 319 51 328 48 327 42 337 34 Area code 856 poly 248 1 257 11 265 35 253 43 264 50 258 64 278 67 286 56 294 54 305 58 328 47 324 41 335 35 322 30 304 -2 Area code 484 poly 85 65 88 53 101 43 109 48 111 33 100 12 94 4 100 -1 245 -1 258 12 266 35 250 43 263 50 256 66 Area code 717 poly 36 1 43 9 38 19 37 29 17 44 14 67 84 66 87 53 101 44 106 48 111 35 96 5 96 -1 Area code 814 poly 2 2 0 65 16 68 18 43 39 30 40 17 45 10 35 2 Area code 724 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 poly 336 153 335 186 288 188 277 69 286 56 294 55 303 57 298 76 299 88 316 129 Area code 302 poly 337 190 327 226 278 242 235 193 219 187 214 168 211 157 211 135 205 121 201 116 198 109 200 105 173 94 175 86 167 66 275 67 288 188 Area codes 410, 443, and 667 poly 0 68 -1 184 16 191 22 186 38 151 51 159 85 118 88 103 87 90 125 121 133 106 135 97 129 92 128 87 122 84 126 81 126 75 116 77 104 68 98 69 93 75 86 73 81 77 79 84 69 84 61 81 59 76 59 73 54 74 43 93 37 88 32 87 31 94 4 117 5 67 Area code 304/681 poly 247 250 249 239 221 220 214 212 200 213 189 199 184 211 169 211 142 226 121 223 106 243 113 248 Area code 804 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

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

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Area codes 410, 443, and 667 are telephone area codes in the North American Numbering Plan (NANP) for the eastern half of the U.S. state of Maryland. The numbering plan area (NPA) includes the Baltimore metropolitan area 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 from area code 301 in 1991. 443 and 667 found assignment primarily in cellular service and for competitive local exchange carriers, such as Comcast and Cavalier Telephone, when introduced, but have since become universal in carrier availability.

History

In 1947, the American Telephone and Telegraph Company (AT&T) published the first configuration of a nationwide telephone numbering plan 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. (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 machines and pagers 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'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), 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, 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 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.Шаблон:Efn Effective November 1, 1991, ten-digit dialing 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 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 ten-digit dialing. 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:

Шаблон:Col-begin Шаблон:Col-break In the Baltimore metropolitan area:

• All of Baltimore City and Baltimore, Calvert and Harford counties
• Most of Anne Arundel, Carroll and Howard countiesШаблон:Efn
• A small portion of eastern Frederick CountyШаблон:Efn

Шаблон:Col-break 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

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