Area Code 360

Its numbering plan area (NPA) comprises all of western Washington outside urban King, Pierce, and Snohomish counties and Bainbridge Island, Until January 15, 1995, when the area code commenced service, the numbering plan area (NPA) was served by area code 206, Washington's original area code since 1947.

Since 2017, area code 360 has been an overlay area code, from the addition of area code 564 to the same numbering plan area. Area code 564 is slated for overlay onto additional NPAs in the region, when numbering shortages demand relief.

From 1947 to 1957, all of Washington state was assigned area code 206 for routing long-distance telephone calls in Operator Toll Dialing. In 1957, the numbering plan area (NPA) was reduced to just the western part of the state, west of the Cascade Mountains, dividing the state into two calling areas. 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.

Numbering plan area 360 consists of two sections that are the result of numbering disputes in the community. The configuration arose when residents of several Seattle exurbs protested the loss of area code 206 and changing to 360. In response, US West reassigned some central offices back to 206. However, 206 was under numbering pool pressure even after the creation of 360 and the restoration of these exurbs forced the Washington Public Utilities Commission to switch most of Seattle's suburban ring into areas 253 and 425 in 1998, sooner than originally planned.

This made 360 one of the few NPAs in the North American Numbering Plan without a continuous land border; others include 706 in Georgia, 423 in Tennessee and 386 in Florida. Each case results from a split that removed the middle from a formerly contiguous area.

In 1999, the Washington Utilities and Transportation Commission intended to overlay 360 with an additional area code, but the implementation was delayed indefinitely. A 2016 report forecasted exhaustion in 2018. The change was finally approved in May 2016. On August 28, 2017 numbering plan area 360 was assigned the second area code, 564, to form an overlay numbering plan. Since July 29, 2017, all calls in western Washington require ten-digit dialing; the first 564 prefix was assigned in 2021.

The new area code 564 is intended to eventually overlay other western Washington NPAs (206, 253, and 425) when demand requires numbering relief action.

Area codes 360 and 334 (Alabama), which began service on the same day, were the first two area codes in the North American Numbering Plan with a middle digit other than 0 or 1.

The larger, western portion stretches from the Strait of Juan de Fuca to the Oregon border, while the portion on the east shore of Puget Sound stretches from the border with British Columbia, Canada, almost to Everett.

Cities and towns in the numbering plan area include:

• List of Washington (state) area codes
• List of North American Numbering Plan area codes