The first historical society was formed about 1916, revived in 1924, and ceased to exist in 1954. The present society was organized in 1959 as part of the Decatur County sesquicentennia observance. The purpose of the society is:

To discover, procure, & preserve documents, papers, books, articles, & things that may relate to the natural, civil, literary, and ecclesiastical history of the State of Indiana & to the county of Decatur in particular, and to establish and maintain collections in art and archaeology. To establish a museum in order to exhibit & preserve objects of permanent interest in the history of the United States, the State of Indiana, & Decatur County. To preserve objects of permanent interest in the arts & sciences. To promote a general interest in the history of our country and the people thereof.