See RCW 29A.36.071
“If the local governmental unit is a city or a town, or if the ballot title is for a referendum under RCW 35.13A.115, the concise statement must be prepared by the city or town attorney. If the local governmental unit is a county, the concise statement must be prepared by the prosecuting attorney of the county. If the unit is a unit of local government other than a city, town, or county, the concise statement must be prepared by the prosecuting attorney of the county within which the majority area of the unit is located.“