Area Code Atlas

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.

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.

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 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.