Fanning's Illustrated Gazetteer of the United States.... (New York: Phelps, Fanning & Co., 1853), 93.
COOK COUNTY, situated on the easterly boundary of Illinois, on the west side of Lake Michigan, and watered by Des Plaines, Chicago, and Du Page rivers. Area, 864 square miles. Face of the country generally level, containing prairies; soil fertile. Seat of justice, Chicago. Pop. in 1835, 7,500; in 1840, 10,201; in 1850, 43,385.