The Franklin County Jail, located at 209 W. Main St. in Benton, is the former county jail of Franklin County, Illinois. The jail was built in 1905–06 to replace the county's previous jail, which was built in the 1840s after the county seat moved to Benton. Architect Joseph W. Royer designed the jail; the brick building features limestone trim, a hip roof with gabled dormers, and a front porch which was rebuilt in 1997. The building also included the county sheriff's residence, an arrangement which allowed for the sheriff to continuously watch the prisoners. The jail housed prisoners until 1990, when a new jail was constructed after the State of Illinois condemned the old building. The Franklin County Historic Preservation Society has since converted the old jail to a historic museum.