Waterloo, IL -- U.S. city in Illinois Population (2000): 7614 Housing Units (2000): 3015 Land area (2000): 5.566509 sq. miles (14.417192 sq. km) Water area (2000): 0.050945 sq. miles (0.131947 sq. km) Total area (2000): 5.617454 sq. miles (14.549139 sq. km) FIPS code: 79150 Located within: Illinois (IL), FIPS 17 Location: 38.335243 N, 90.152685 W ZIP Codes (1990): 62298 Note: some ZIP codes may be omitted esp. for suburbs. Headwords: Waterloo, IL Waterloo