Area code 564

From 1947 to 1957, all of Washington state was assigned area code 206 for routing long-distance telephone calls in Operator Toll Dialing.

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.

By the late 1990s, projections indicated possible exhaustion once again, so that in 1999, area code 564 was assigned for installation as an overlay of NPA 360, with an in-service date of August 1, 2000.

On August 22, 2001, the WUTC announced that increased efficiency in the reuse of the existing number pool meant that the immediate need for the new area code had subsided.

[1] Per NANPA analysis and determination, the overlay complex may be extended only as needed when NPAs 206, 253, or 425 are nearing exhaustion.