61081 -- U.S. ZIP code Municipality (1990): STERLING, Illinois All ZIPs for this municipality (1990): 61081 Population (2000): 22844 Housing Units (2000): 9365 Land area (2000): 126.640889 sq. miles (327.998383 sq. km) Water area (2000): 0.122118 sq. miles (0.316285 sq. km) Total area (2000): 126.763007 sq. miles (328.314668 sq. km) Located within: Illinois (IL) Location: 41.813776 N, 89.705373 W