Wash. Rev. Code § 36.34.140
The board of county commissioners, if it appears that it is for the best interests of the county and the people thereof, that any county real property and its appurtenances should be leased for a year or a term of years, may lease such property under the limitations and restrictions and in the manner provided in this chapter, and, if it appears that it is for the best interests of the county and the people thereof, that any county real property and its appurtenances which is now being, or is to be devoted to airport or aeronautical purposes or purposes incidental thereto, should be leased for a year or a term of years, said board of county commissioners may lease such property under the limitations and restrictions and in the manner provided in this chapter, and said board of county commissioners shall have power to lease such county real property and its appurtenances whether such property was heretofore or hereafter acquired or whether heretofore or hereafter acquired by tax deed under tax foreclosure proceedings for nonpayment of taxes or whether held or acquired in any other manner. Any lease executed under the authority of the provisions hereof creates a vested interest and a contract binding upon the county and the lessee.
RCW 36.34.140