Area Code Atlas

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.

NANP-EXTENSION OF PERMISSIVE DIALING FOR 360 NPA (WASHINGTON STATE)

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- Overlay of 360 Numbering Plan Area (NPA) with 564 NPA (Washington)

NPA 564 planned as overlay for 360

Area code 564 was first proposed in 1999 to relieve number shortages in area code 360, with an initial planned in-service date of August 1, 2000.

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.

Overlay planned for NPA 360 with new code 564

The Washington Utilities and Transportation Commission approved the overlay of area code 360 with a new area code 564 in May 2016 to provide numbering relief for western Washington.

Order adopting implementation plan for 564 overlay

The Washington Utilities and Transportation Commission adopted an implementation plan in 2016 to activate area code 564 as an overlay for area code 360.

NPA 564 overlay on 360 announced

NPA 564 to Overlay NPA 360 (Washington)

Overlay of area code 564 in Washington

In 2017, area code 564 was introduced as an overlay for the 360 area code region in Western Washington due to number exhaustion, allowing new numbers to be assigned with 564 in the same geographic area.

Ten-digit dialing mandatory in western Washington

Ten-digit dialing became mandatory for all of western Washington in 2017, coinciding with the introduction of the 564 overlay.

Permissive 10-digit dialing begins for 206, 253, 360, 425, and 564 (specific to 360 and overlay)

Permissive 10-digit dialing began on January 28, 2017, for area codes 206, 253, 360, 425, and the new overlay 564, allowing both 7-digit and 10-digit dialing during the transition. This includes specific permissive dialing for the 360 area code and the 564 overlay region.

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 overlay activated on NPA 360

Area code 564 was activated as an overlay on area code 360 on August 28, 2017, requiring ten-digit dialing for all calls in western Washington.

Area code 564 numbers issued in 360 region

Telephone numbers with area code 564 began to be issued in the existing 360 numbering plan area starting September 30, 2017.