On September 19, 1925, the Greene County Historical Society was incorporated with the original mission of “collecting and preserving books, papers, records, writings and relics, legal, civil, military and otherwise, relating to the history of Greene County, Pennsylvania and adjacent counties.” At first, the Greene County Historical Society was housed in one room in the basement of the then recently built Long Building. As the collections grew, the Historical Society purchased an adjoining room in 1956 to use as a library and board room and even stored some artifacts and archives at board member homes.
In 1969, the Historical Society leased the Greene County Home, which was no longer fit for use as a home for the indigent, and a year later opened the library. In June of 1971, the museum was opened to the public. Now, GCHS maintains a 52 room museum with over a thousand artifacts that represent all aspects of Greene County and surrounding areas history and culture.