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image:Area code 301.png|right|300px|thumb|alt=area codes 240 and 301|Maryland consists of the red and blue areas. The red area indicates area codes 240 and 301. This map is clickable; click on any neighboring area code to go to the page for that code. poly 336 37 323 30 310 13 305 -2 337 2 Area code 215 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 code 757 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 # desc bottom-left 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 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. The main area code, 301, was one of the original area codes established in 1947, and originally covered the entire state of Maryland. This was somewhat unusual, given that Maryland 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 1990, 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 a local access and transport area (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 also existed in the District's 202, essentially using 202 for the entire metro. One consequence of this was that no prefixes could be duplicated in the D.C. area. For instance, if 202-574 was in use in the District or 703-574 was being used in Northern Virginia, the corresponding 301-574 exchange could only be used in Maryland in areas a safe distance from the Washington metro area such as the Eastern Shore. By the end of the 1980s, the D.C. area was running out of prefixes. To free up available numbers, the suburban use of 202 was ended in 1990. 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. It was apparent that breaking seven-digit dialing in the Washington area would not free up enough numbers to stave off the immediate need for a new area code. 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, 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, 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 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 2020. Counties served by these area codes include: *Allegany *Charles *Frederick *Garrett *Howard (shared with 410/443/667) *Montgomery *Prince George's *St. Mary's *Washington *A very small portion of southwestern Carroll County (shared with 410/443/667) Local calls require 10-digit dialing (area code + number, leading "1" is not required). ==Notes== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Area codes 240 and 301」の詳細全文を読む スポンサード リンク
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