Washington County Museum is a history museum located in downtown Hillsboro, Oregon, United States. Opened in 1975, the museum is operated by the Washington County Historical Society with a mission of preserving the history of the area. The museum moved the main exhibit space to downtown Hillsboro at the Civic Center in November 2012. The prior museum space remains as a research library at Portland Community College's Rock Creek Campus and as home to the original Washington County Jail built in 1853.