Highland County, OH neighbors Clinton near Hillsboro metropolitan centre yielding a 2020 estimated census population standing at 43,239 making it the 23rd highest populous county situated hereabouts. Its county seat is Hillsboro with other towns include Leesburg & Greenfield-Hillsboro itself corresponds out to Highland’s biggesttown aside from acknowledged country seat. This area had been established from Ross and Adams Counties back in 1805 when local residents petitioned for new administrative boundaries - posthumously named after Scotland Highlands commanding during era Thomas Jefferson .