Wash. Rev. Code § 37.04.020
Concurrent jurisdiction with this state in and over any land so acquired by the United States shall be, and the same is hereby, ceded to the United States for all purposes for which the land was acquired; but the jurisdiction so ceded shall continue no longer than the United States shall be the owner of such lands, and if the purposes of any grant to or acquisition by the United States shall cease, or the United States shall for five consecutive years fail to use any such land for the purposes of the grant or acquisition, the jurisdiction hereby ceded over the same shall cease and determine, and the right and title thereto shall revest in this state. The jurisdiction ceded shall not vest until the United States shall acquire title of record to such land.
RCW 37.04.020