Fanning's Illustrated Gazetteer of the United States.... (New York: Phelps, Fanning & Co., 1853), 82.
CLARK COUNTY, situated on the eastern boundary of Illinois, on the west side of Wabash river. Area, 500 square miles. Seat of justice, Marshall. Pop. in 1830, 3,124; in 1840, 7,453; in 1850, 9,532.