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25:
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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
275:
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
258:
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
137:
267:), 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
234:), 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
326:, 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.
129:
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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
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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,
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318:. 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.
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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
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877:
872:
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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.
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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
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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
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Area code 410 officially entered service on
October 6, 1991; it was initially implemented in a permissive-dialing phase, with
57:
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108:
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857:
271:, many of the same factors resulted in most of the old 703 territory outside of Northern Virginia split off as
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46:
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for local calls across the new 301/410 boundary. The split largely followed metro lines. However, slivers of
82:
366:
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159:
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226:. Despite the state being home to two large metropolitan areas, Baltimore and the Maryland suburbs of
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for one numbering plan area, among which 410 was the initial area code for the NPA, when it was
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671:
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8:
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placed the numbering resources in the danger of exhaustion of central office prefixes.
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capacity of central office prefixes could not be used for each involved area code.
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202:, when introduced, but have since become universal in carrier availability.
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in 1991. 443 and 667 found assignment primarily in cellular service and for
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and pagers, particularly in and around
Baltimore. To solve this problem,
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List of cities covered and exchanges from Area-Codes.com, 443 Area Code
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List of cities covered and exchanges from Area-Codes.com, 410 Area Code
484:
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24:
816:
766:
688:
299:, a Washington exurb, switched to 410. Effective November 1, 1991,
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was required when calling a different area code in
Maryland.
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214:(AT&T) published the first configuration of a nationwide
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exchanges 210, 317, 490, 497, 498, 596, 604, 725, and 778,
472:
Four counties were split between area code 301 and 410.
606:"Maryland's new 667 area code goes into effect in 2012"
475:
Anne
Arundel County was assigned area code 410, except
49:. Unsourced material may be challenged and removed.
533:"Nation-Wide Operator Toll Dialing—the Coming Way"
490:Carroll County was assigned area code 410, except
334:The counties served by these area codes include:
883:Telecommunications-related introductions in 2012
878:Telecommunications-related introductions in 1997
873:Telecommunications-related introductions in 1991
849:
500:Frederick County remained area code 301, except
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573:
571:
170:. The numbering plan area (NPA) includes the
686:
603:
568:
530:
147:'s area codes highlighted in red and blue
109:Learn how and when to remove this message
604:Fazeli Fard, Maggie (October 12, 2011).
524:
254:. This was accomplished via a system of
212:American Telephone and Telegraph Company
122:
468:
466:
464:
850:
633:"2022-1 NRUF and NPA Exhaust Analysis"
577:"New area code for eastern Maryland".
16:Telephone area codes for east Maryland
342:In the Baltimore metropolitan area:
291:counties, as well as much of western
649:from the original on October 9, 2022
494:exchange 829 remained area code 301.
461:
337:
47:adding citations to reliable sources
18:
192:competitive local exchange carriers
162:(NANP) for the eastern half of the
13:
14:
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531:Mabbs, Ralph (Winter 1947–1948).
672:NANPA area code map of Maryland
23:
863:Area codes in the United States
34:needs additional citations for
625:
597:
590:"Now Area Codes Count in Md."
584:
555:
508:exchange 635 was assigned 410.
256:central office code protection
58:"Area codes 410, 443, and 667"
1:
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160:North American Numbering Plan
152:Area codes 410, 443, and 667
7:
868:Communications in Baltimore
565:. November 21, 1990. p. E6.
380:A small portion of eastern
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178:. The three area codes are
172:Baltimore metropolitan area
10:
899:
594:. November 2, 1992. p. B9.
581:. November 1, 1991. p. 1A.
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561:"New area code coming".
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394:Maryland's Eastern Shore
216:telephone numbering plan
537:Bell Telephone Magazine
858:Area codes in Maryland
148:
220:Operator Toll Dialing
143:
43:improve this article
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611:The Washington Post
592:The Washington Post
421:Queen Anne's County
687:
483:exchange 952, and
200:Cavalier Telephone
149:
846:
845:
640:nationalnanpa.com
579:The Baltimore Sun
563:The Baltimore Sun
504:exchange 775 and
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411:Dorchester County
316:ten-digit dialing
301:ten-digit dialing
281:ten-digit dialing
248:Northern Virginia
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441:Worcester County
382:Frederick County
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297:Frederick County
228:Washington, D.C.
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436:Wicomico County
426:Somerset County
401:Caroline County
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745:Atlantic Ocean
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666:External links
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642:. April 2022.
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431:Talbot County
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293:Howard County
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276:before 1990.
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273:area code 540
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269:Potomac River
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232:area code 202
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224:area code 301
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210:In 1947, the
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188:area code 301
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180:overlay codes
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176:Eastern Shore
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60: –
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55:
54:Find sources:
48:
44:
38:
37:
32:This article
30:
26:
21:
20:
819:area codes:
780:area codes:
778:Pennsylvania
769:area codes:
753:
736:
732:410/443/667
731:
722:
705:
696:
691:area codes:
653:November 30,
651:. Retrieved
639:
627:
615:. Retrieved
609:
599:
591:
586:
578:
562:
557:
545:. Retrieved
540:
536:
526:
502:Union Bridge
445:
406:Cecil County
391:
386:
367:Anne Arundel
341:
333:
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320:
311:
305:
285:Anne Arundel
278:
261:
244:
236:fax machines
209:
151:
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120:
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72:
65:
53:
41:Please help
36:verification
33:
794:610/484/835
782:215/267/445
727:301/240/227
714:484/610/835
697:410/443/667
693:301/240/227
506:New Windsor
416:Kent County
308:cell phones
852:Categories
518:References
492:Mount Airy
485:Fort Meade
194:, such as
164:U.S. state
156:area codes
69:newspapers
352:Baltimore
348:Baltimore
817:Virginia
767:Delaware
689:Maryland
644:Archived
617:July 23,
547:July 20,
543:(4): 181
481:Marlboro
377:counties
365:Most of
362:counties
330:Coverage
174:and the
168:Maryland
145:Maryland
841:804/686
837:757/948
833:703/571
829:540/826
806:814/582
798:717/223
790:570/272
758:757/948
710:717/223
392:All of
371:Carroll
360:Harford
356:Calvert
346:All of
289:Carroll
265:Verizon
206:History
196:Comcast
158:in the
83:scholar
477:Laurel
446:
375:Howard
240:pagers
85:
78:
71:
64:
56:
754:South
706:North
647:(PDF)
636:(PDF)
455:Notes
186:from
184:split
90:JSTOR
76:books
737:East
723:West
655:2022
619:2012
549:2023
373:and
358:and
350:and
287:and
238:and
218:for
198:and
62:news
825:434
821:276
810:878
802:724
786:412
771:302
741:302
252:703
250:'s
166:of
45:by
854::
839:,
835:,
831:,
827:,
823:,
808:,
804:,
800:,
796:,
792:,
788:,
784:,
756::
743:,
739::
725::
712:,
708::
695:,
638:.
608:.
570:^
541:26
539:.
535:.
463:^
396::
369:,
354:,
657:.
621:.
551:.
230:(
112:)
106:(
101:)
97:(
87:·
80:·
73:·
66:·
39:.
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