Wash. Rev. Code § 58.28.220
The judge of the superior court of any county in this state, whenever he or she is so requested by a petition signed by not less than five residents, householders in any such unincorporated town, whose names appear upon the assessment roll for the year preceding such application in the county wherein such unincorporated town is situated-which petition shall set forth the existence, name, and locality of such town, whether such town is situated on surveyed or unsurveyed lands, and if on surveyed lands an accurate description according to the government survey of the legal subdivisions sought to be entered as a government townsite must be stated; the estimated number of its inhabitants; the approximate number of separate lots or parcels of land within such townsite, and the amount of land to which they are entitled under such acts of congress-must estimate the cost of entering such land, and of the survey, platting, and recording of the same, and must endorse such estimate upon such petition, and upon receiving from any of the parties interested the amount of money mentioned in such estimate, the said judge may cause an enumeration of the inhabitants of such town to be made by some competent person, exhibiting therein the names of all persons residing in said proposed townsite and the names of occupants of lots, lands, or premises within such townsite, alphabetically arranged, verified by his or her oath, and cause such enumeration to be presented to such judge.
RCW 58.28.220