On January 26, 1907, at 2 p.m., a group of interested citizens of the county held an organizational meeting in the Supervisors Room of the courthouse for the purpose of forming a LaSalle County Historical Society.
About 60 persons of the county met with Terry Simmons of Marseilles acting as chairman. They adopted a constitution for the Society and elected Horace Hall of Ottawa as the first president.
The Society obtained its certificate of incorporation under the General Not-For-Profit Corporation Act of the State of Illinois on September 5, 1924, under the name of LaSalle County Historical Society. The purpose of the Society was set forth: “To search out, procure and preserve in permanent form, facts and data in the history of the County of LaSalle, Illinois, as related to persons, places and all objects therein.”