The Johnson County Historical Society formed in 1958 and serves as an important center for helping residents of Johnson County and those interested in Johnson County history understand the significance of the county's past.
The Johnson County Missouri Historical Society is made up of a complex of modern and historic structures, which help preserve and tell the story of the county's past. The Mary Miller Smiser Heritage Library and Museum serves as the official repository of collections related to Johnson County Missouri. It also features museum exhibits that tell the history of the county.
In addition to the Smiser Library and Museum, the historical society also manages the Old Courthouse. The Old Courthouse was built in 1838 and remained in use until 1871, when the county business moved to the Courthouse on Holden Street. It was at this courthouse where George Graham Vest delivered his "Eulogy of the Dog" speech.
In addition to the courthouse, the historical society also manages the Elm School. The school is an early 20th century one-room school that was originally located in western Johnson County, but was relocated to the site in 1996 so that the historical society could interpret the significance of the structure to the public.