Wash. Rev. Code § 35.60.020
The participation of any municipality in any world fair or exposition, whether held within the boundaries of such municipality or within the boundaries of another municipality; the purchase, lease, or other acquisition of necessary lands therefor; the acquisition, lease, construction, improvements, maintenance, and equipping of buildings or other structures upon such lands or other lands; the operation and maintenance necessary for such participation, and the exercise of any other powers herein granted to such municipalities, are hereby declared to be public, governmental, county and municipal functions, exercised for a public purpose, and matters of public necessity, and such lands and other property acquired, constructed, improved, maintained, equipped, used, and disposed of by such municipalities in the manner and for the purposes enumerated in this chapter shall and are hereby declared to be acquired, constructed, improved, maintained, equipped, used, and disposed of for public, governmental, county, and municipal purposes and as a matter of public necessity.
RCW 35.60.020