Fanning's Illustrated Gazetteer of the United States.... (New York: Phelps, Fanning & Co., 1853), 82.
CLARK COUNTY, situated at the northeast comer of Missouri, with Des Moines river on the northeast, and the Mississippi on the east. Soil generally fertile. Area, 560 square miles. Seat of justice, Waterloo. Pop. in 1840, 2,846; in 1850, 5,527.