Area Code Atlas

NPA 206 introduced for all of Washington

Area code 206 was one of the original North American area codes assigned in 1947 and originally served the entire state of Washington.

NPA 509 assigned to eastern Washington

Area code 509 was assigned in 1956 when it was split from area code 206, covering the eastern part of Washington state including Spokane and the Tri-Cities.

NPA 509 split from 206

In 1957, area code 206 was reduced to cover only western Washington, while area code 509 was created to serve most of eastern Washington. The split, a flash-cut, assigned the eastern two-thirds of Washington to 509 and roughly followed the Cascade Mountains.

NANP - INTRODUCTION OF INTERCHANGEABLE CENTRAL OFFICE CODES IN THE 206 NPA

NANP-SPLIT OF 206 (WASHINGTON STATE) NUMBERING PLAN AREA (NPA)

NPA 360 split from 206 for western Washington

In 1995, area code 360 was created in a split from 206, serving most of western Washington outside the Seattle and Tacoma metropolitan areas. This was one of the first area codes in the U.S. with a middle digit other than 0 or 1.

NPA 360 split from 206

On January 15, 1995, area code 360 was activated, splitting most of western Washington outside the Seattle/Tacoma area from 206. This new area code was one of the first in North America not conforming to the traditional N0X/N1X format, causing issues for some long-distance and private telephone systems. A permissive dialing period allowed continued use of 206 for affected areas until May 21, 1995.

Permissive dialing period for 206/360 split begins

Following the activation of area code 360 on January 15, 1995, a permissive dialing period began, allowing calls to western Washington to be completed using either 206 or 360. This transition period was implemented to address technical issues and allow time for systems to adapt. During the transition, callers could still reach Western Washington numbers by dialing area code 206. The transition period lasted until May 21, 1995.

Seattle exurbs returned to 206 after 360 split

Shortly after the 360 split in January 1995, several Seattle exurbs were returned to area code 206 following resident protests. The cities of Des Moines and Woodway were split between area codes due to switching center constraints.

Some Seattle exurbs were returned from 360 to 206

After protests from residents in the Seattle exurbs, US West returned some exurban territory to area code 206 shortly after the 360 split.

Mandatory use of 360 for calls outside Tacoma-Seattle-Everett

On May 21, 1995, the permissive dialing period ended, and callers were required to use area code 360 for numbers outside the Tacoma-Seattle-Everett area. Calls using 206 to reach these numbers were no longer completed.

NANP-Split of 206 (Washington State) Numbering Plan Area (NPA)

NPA 253 split from 206

In 1997, area code 253 was created from a split of 206, serving the southern portion of the Seattle metropolitan area, including Tacoma.

NPA 425 split from 206

In 1997, area code 425 was created from a split of 206, serving the northern and eastern suburbs of Seattle, including Everett and the Eastside.

NPAs 253 and 425 split from 206

A three-way split of the 206 territory took effect on April 25, 1997. The southern portion, including Tacoma, received area code 253, while the northern portion, including Everett and the Eastside, received 425.

Permissive dialing period for 206/253/425 split begins

A permissive dialing period began on April 27, 1997, allowing callers in the affected regions to use either the new area codes (253 and 425) or the existing 206 code for local calls. This transition period was intended to ease the adjustment to the new codes and lasted for seven months.

NPA 206 reduced in three-way split creating 253 and 425

Area code 206 was reduced in size on April 27, 1997, when a three-way split created area codes 253 and 425. Area code 425 was created from the northern and eastern suburbs of Seattle, including Bellevue and Redmond, while 206 remained for central Seattle. The split was prompted by number exhaustion due to increased demand from faxes, modems, and cellular phones, with a permissive dialing period allowing continued use of 206.

Mandatory 10-digit dialing for 253 and 425

On November 16, 1997, mandatory 10-digit dialing was implemented for local calls in the regions affected by the 206 split, requiring callers to use the new area codes 253 and 425. This change affected residents in areas such as Woodway and Shoreline, with some towns split between area codes due to switching center constraints. The transition marked the end of the permissive dialing period following the split of area code 206.

Des Moines and Woodway were split between NPAs after relief changes

As part of the reintegration and later relief configuration, the cities of Des Moines and Woodway were split between area codes because of switching-center capacity and boundary constraints.

NPA 253 split from 206

Area code 253 was created in 1998 as part of a reconfiguration of the Seattle suburban ring, splitting from area code 206 due to numbering resource exhaustion.

NPA 425 split from 206

Area code 425 was created in 1998 as part of a reconfiguration of the Seattle suburban ring, splitting from area code 206 due to numbering resource exhaustion.

NPA 564 to Overlay NPAs 206, 253, 360, and 425 (Washington)

NPA 564 overlay plan expanded to include 206, 253, and 425

The overlay plan for area code 564 was expanded in 2000 to include the metropolitan Seattle area codes 206, 253, and 425, anticipating exhaustion in those NPAs.

Area code 564 planned as overlay for 206, 253, and 425

Since 2017, area code 564 has been planned to overlay area codes 206, 253, and 425 in Washington state to provide relief when central office code exhaustion demands it.

Mandatory ten-digit dialing begins in western Washington

Mandatory ten-digit dialing began on July 29, 2017, for all calls in western Washington, including area codes 206, 253, 360, 425, and the new overlay 564.

NPA 564 planned to overlay 253, 206, and 425

Area code 564, first activated as an overlay for 360 in 2017, is planned to overlay additional area codes in western Washington, including 253, 206, and 425, when number exhaustion requires relief.

Expansion of 564 overlay approved to include 206 in Seattle area

On June 15, 2023, the Washington Utilities and Transportation Commission approved the expansion of area code 564 to overlay the 206 numbering plan area, extending the overlay to metropolitan Seattle to address projected number exhaustion in 2025.

NPA 564 overlay on 206 announced

NPA 564 to Overlay NPA 206 (Washington)

NPA 564 overlays 206

On June 10, 2025, the 564 area code was expanded to overlay the 206 numbering plan area in the Seattle region. This expansion allowed new numbers to be assigned with 564 following the exhaustion of available 206 central office codes. Providers began activating central office codes for 564 in the 206 area once all 206 codes had been allocated.