Fanning's Illustrated Gazetteer of the United States.... (New York: Phelps, Fanning & Co., 1853), 173.
JEFFERSON COUNTY, situated on the easterly boundary of Missouri, with Mississippi river on the east. Area, 500 square miles. Face of the country broken; soil generally sterile. Seat of justice, Hillsborough. Pop. in 1820, 1,835; in 1830, 2,586; in 1840, 4,296; in 1850, 6,928.