The society manages a research libray as well as the McCoy House Museum, the birthplace of Major General Frank Ross McCoy in 1874.
The Mifflin County Historical Society, founded in 1921, had become known as "Frysinger' s Dream". The founder George R. Frysinger had served as a Civil War editor of the Lewistown Gazette and ended his years of affiliation with the Society as the President Emeritus. The McCoy home now serves as the museum of Mifflin County as well, containing the permanent collections of the area. The house is listed on the National Register of Historic Places and the Pennsylvania Heritage Trail.