Classification: County
Located in: Illinois (IL)
Total Population (2000): 18735
Total Housing Units (2000): 7787
Land Area (square meters): 1405122319
Water Area (square meters): 1674618
Land Area (square miles): 542.520783
Water Area (square miles): 0.646574
Latitude (decimal degrees): 40.876975
Longitude (decimal degrees): -90.622695
FIPS Code: 17
Place FIPS Code: 187