Chapter 35A.15 RCW outlines the disincorporation process for a code city. Disincorporation can be initiated either through a petition signed by a majority of the registered voters in the city or by resolution of the council. See RCW 35A.15.010. The proposition is then submitted to the voters at the next general election pursuant to RCW 35A.15.020. If the city has any indebtedness or outstanding liabilities, it shall order the election of a receiver at the same time. Per RCW 35A.15.050, the effects of disincorporation are set forth at RCW 35.07.090, 35.07.100, and 35.07.110. The disincorporation process for non-code cities and towns is at Chapter 35.07 RCW.
Our understanding is that the most recent town or city to disincorporate was Westlake (in Grant County) in 1972. In 2023, my colleague confirmed this with staff at the Association of Washington Cities (AWC). There is useful research and analysis in this Disincorporation Memorandum from Spokane Valley (2009).
Upon disincorporation, the powers and authority of the city are gone, and the area is controlled as any other unincorporated area of the county. From a practical standpoint, disincorporation results in a loss of local control for residents of the area. Their local elected representatives become the county elected officials. An important issue to consider is whether and to what extent the county will be able to provide the services previously provided by the city.