Harrison County, OH borders Jefferson near Cadiz metropolitan centre granting a 2020 estimated census population standing at 15,856 making it the 46th most populous county situated within Ohio overall. Its county seat is Cadiz with other towns include Jewett & Tippecanoe-Cadiz itself corresponds out to Harrison's biggesttown aside from recognized country seat. This area had been established from Jefferson and Tuscarawas Counties back in 1813 when local residents petitioned for new administrative boundaries - posthumously named after General William Henry Harrison ruling period Thomas Jefferson .