Includes offices for Superior Court, Clerk, District Court, Assessor, Auditor, Commissioners, Prosecutor, Sheriff, Treasurer, MIS, and WSU Ext Office. History: Douglas County was created in 1883 and named after U.S. Senator Steven Douglas of Illinois who was the chairman of the U.S. Commission on Territories when the Territory of Washington was created. Waterville was designated the County Seat in 1886 and the current Courthouse was initially constructed in 1905.