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130:. This configuration remained in place until 1995, when resource pressure from the proliferation of cell phones, fax machines, and pagers required additional central office prefixes and telephone numbers. Most of the region outside the Seattle and Tacoma areas was split from 206 to form a new numbering plan area with area code 360.
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The WUTC took further steps to decrease the need for new number blocks in 360 and 509 and head off the need for new area codes, including aggressive reclamation of unused and underused number blocks and exchanges. The introduction of mandatory
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Per NANPA analysis and determination, the overlay complex may be extended only as needed when NPAs 206, 253, or 425 are nearing exhaustion. Exhaustion of area code 206 is expected for 2025, while 253 and 425 are nowhere near exhaustion.
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have rejected the telephone companies' request for a new area code and instead directed them to actively share and efficiently use the number blocks that had already been assigned. That refers mainly to the practice of
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were slated for expansion of the overlay upon exhaustion of central office codes in each NPA. In 2023, area code 206 was approved for expansion with a guide line for preparation of inclusion of at least nine months.
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According to the WUTC's estimate as of March 2014, the earliest projection for any
Western Washington area code to be exhausted was 2018 for area code 360. The other codes were not expected to exhaust before 2025.
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By the late 1990s, projections indicated possible exhaustion once again, so that in 1999, area code 564 was assigned for installation as an overlay of NPA 360, with an in-service date of August 1, 2000.
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prefix in ten blocks of one thousand telephone numbers for more efficient allocation, rather than assigning a prefix's whole numbering space (10,000 numbers) to one carrier in a single
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Area code 564 was finally implemented on August 28, 2017. Ten-digit dialing had been mandatory since July 29, 2017, for all local calls in
Western Washington.
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Since
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On June 15, 2023, the WUTC approved expanding the coverage of area code 564 to include numbering plan area 206.
185:(a prerequisite for number pooling) has also served to stem the demand for new numbers and thus new area codes.
381:"In the Matter of the Implementation of the 564 Numbering Plan Area: Order Adopting Implementation Plan (PDF)"
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254:"Planning Letter PL-196: NANP-Overlay of 360 Numbering Plan Area (NPA) with 564 NPA (Washington)"
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279:"Planning Letter PL-239: NPA 564 to Overlay NPAs 206, 253, 360, and 425 (Washington)"
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81:. The area code was first proposed in 1999 to relieve telephone number shortages in
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433:"Planning Letter PL-492: NPA 564 to Overlay NPA 360 (Washington)"
356:"Planning Letter PL-492: NPA 564 to Overlay NPA 360 (Washington)"
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336:. Washington Utilities and Transportation Commission. March 2016
304:"Planning Letter PL-298: Suspension of 564 Overlay (Washington)"
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408:"Meet area code 564: The new kid in town is gaining ground"
141:(WUTC) projected that the metropolitan Seattle area codes (
122:. In 1957, the numbering plan area (NPA) was split, with
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Telephone area code for western
Washington, United States
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From 1947 to 1957, all of
Washington state was assigned
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334:"Washington State Area Codes and Numbering Issues"
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217:List of North American Numbering Plan area codes
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240:"New area code coming to Seattle area"
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453:NANPA area code map of Washington
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622:Area codes in Washington (state)
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259:. NANPA. October 29, 1999
89:. Neighboring area codes
309:. NANPA. August 29, 2001
438:. NANPA. June 28, 2016.
87:numbering plan area 360
361:. NANPA. June 28, 2016
284:. NANPA. July 27, 2000
242:. WUTC. June 15, 2023.
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37:47.60972°N 122.33306°W
120:Operator Toll Dialing
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391:January 30,
171:rate center
73:(NANP) for
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28:122°19′59″W
611:Categories
460:Washington
223:References
25:47°36′35″N
417:March 23,
67:area code
206:See also
600:541/458
596:503/971
564:503/971
365:May 20,
313:May 20,
288:May 20,
263:May 20,
110:History
79:Seattle
69:in the
64:overlay
592:Oregon
149:, and
97:, and
560:South
493:North
436:(PDF)
359:(PDF)
307:(PDF)
282:(PDF)
257:(PDF)
179:local
158:NANPA
547:East
539:564/
514:West
419:2021
393:2017
367:2023
342:2016
315:2023
290:2023
265:2023
181:and
581:604
577:250
551:509
541:360
534:778
530:672
526:250
522:236
505:604
501:250
484:564
480:509
476:425
472:360
468:253
464:206
151:425
147:253
143:206
99:425
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91:206
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Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
