The Washington County Museum was purchased by the Historical Society in 1981. The museum opened in 1983 with two floors of exhibits. It was dedicated on September 14, 1986.
In 1993, the Historical Society members purchased the building south of the museum which now is used for additional exhibits which depict actual shops or factories. This building is called the Museum Annex.
The sheriff residence and jail was donated to the Society in 1997 by the Washington County Commissioners. Built in 1899, at the cost of $8,000, it will be the future home of the Kansas Law Enforcement Museum.