Wash. Rev. Code § 35A.14.460
(1) The legislative body of a county or code city planning under chapter 36.70A RCW and subject to the requirements of RCW 36.70A.215 may initiate an annexation process for unincorporated territory by adopting a resolution commencing negotiations for an interlocal agreement as provided in chapter 39.34 RCW between a county and any code city within the county. The territory proposed for annexation must meet the following criteria:
[ 2003 c 299 s 3.]