Wash. Rev. Code § 53.34.150
Revenue bonds and notes issued under the authority of this chapter are made securities in which all public officers and bodies of this state, all municipalities and municipal subdivisions and all other political subdivisions of this state, all insurance companies and associations and other persons carrying on an insurance business, all banks, bankers, trust companies, savings banks, and savings associations, including savings and loan associations, building and loan associations, investment companies and other persons carrying on a banking business, all administrators, guardians, executors, trustees and other fiduciaries, and all other persons whatsoever who are now or may hereafter be authorized to invest in bonds or other obligations of the state, may properly and legally invest funds, including capital, in their control or belonging to them. Such bonds and notes are also made securities which may be deposited with and shall be received by all public officers and bodies of this state, all municipalities, municipal subdivisions, and other political subdivisions of this state for any purpose for which the deposit of bonds or other obligations of this state is now or may hereafter be authorized.
RCW 53.34.150