Chillicothe is a city in and the county seat of Ross County, Ohio, United States. Located along the Scioto River 45 miles south of Columbus, Chillicothe was the first and third capital of Ohio. It is the only city in Ross County and is the center of the Chillicothe micropolitan area. The population was 22,059 at the 2020 census. Chillicothe is a designated Tree City USA by the National Arbor Day Foundation.