Wash. Rev. Code § 35.02.220
The approval of an incorporation by the voters of a proposed city or town, and the existence of a transition period to become a city or town, shall not remove the responsibility of any county, road district, library district, or fire district, within which the area is located, to continue providing services to the area until the official date of the incorporation. A county shall continue to provide the following services to a newly incorporated city or town, or that portion of the county within which the newly incorporated city or town is located, at the preincorporation level as follows:
[ 1991 c 360 s 9; 1986 c 234 s 22; 1985 c 143 s 1. Formerly RCW 35.21.763.]