List of Washington area codes

Area code 206 is the North American area code for Seattle; nearby Mercer Island, Bainbridge Island and Vashon Island; and portions of the Seattle metro area from Des Moines to Woodway.

Area code 206 was one of the original area codes created in 1947. In 1957, area code 509 was created for the area east of the Cascades in a flash-cut. It split to form area 360 (one of the first 2 area codes not of N0X/N1X form) in 1995, and underwent a 3-way split in 1997 to form areas 253 and 425.

Area code 253 is a telephone dialing code for the suburbs south of Seattle and the South Puget Sound region, centered at Tacoma and extending to include the areas around Gig Harbor, Auburn, and Roy. It currently serves Federal Way and the western half of Pierce County.

The area code went into service on April 27, 1997 as part of a three-way split of area code 206.

Area code 360 is the area code for Western Washington outside the greater Seattle metropolitan area, including the capital, Olympia. It began service on January 15, 1995. The area, which encompasses all of western Washington outside of urban King, Pierce, and Snohomish counties and Bainbridge Island, was previously part of area code 206. The 360 area code was one of the first two area codes that did not take the N1X or N0X form (i.e., the middle digit is neither 0 nor 1) in the North American Numbering Plan, along with Alabama area code 334, which began service on the same day.[2]

Area code 425 is a telephone dialing code for the suburbs north and east of Seattle, particularly the Eastside, extending east to Snoqualmie Summit ski resort (most of which is in Kittitas County),[3] north to Everett, and south to Maple Valley.

The area code went into service on April 27, 1997 as part of a three-way split of area code 206.

Area code 509 is an area code covering Eastern Washington, including Spokane, the Tri-Cities, Yakima, Walla Walla, and Wenatchee. It was created in a split from area code 206 in a flash-cut on January 1, 1957.[4]

Area code 564 is a recently approved area code covering all of Western Washington, including Seattle. It is part of the overlay plan for area codes 206, 253, 360 and 425. This was approved on May 19, 2016 to be implemented starting in the fall of 2017 for new phone numbers.

In 1999, the 564 area code was proposed as an overlay of area code 360, which serves areas of Western Washington outside of the Seattle-Tacoma metropolitan area. This version of the NPA was slated for implementation on July 29, 2000. Later, the Washington Utilities and Transportation Commission (WUTC) determined that the actual increase in need for new numbers in 360 had fallen short of projections, and postponed the NPA until at least February 2001.

In May 2000, the commission projected that the metropolitan Seattle area codes (206, 253, and 425) would also soon exhaust their number pools, and expanded the 564 plan to include those areas as well. By the summer, however, this was determined to be not immediately necessary. The NPA was then planned for application on October 20, 2001.

On August 22, 2001, the WUTC announced that, due to increased efficiency in the reuse of the existing number pool, the immediate need for the new NPA had subsided. Part of this was also attributed to a downturn in the telecommunications sector. The commission put off implementation until no earlier than October 20, 2002.

Since the development of the initial plan for the area code, the WUTC and the NANPA have rebuffed the telephone companies' request for a new NPA and instead directed them to actively share and efficiently use the number blocks already assigned. This mainly refers to the practice of number pooling, or dividing telephone exchanges (aka prefixes) into up to 10 1,000-number blocks, instead of a whole prefix's numbering space being assigned wholesale to one carrier.

Due to the 564 overlay, 10-digit dialing was required for all local phone calls in Western Washington starting July 29, 2017. Before that time, local calls within an NPA could use 7-digit dialing.[5][6]