South Beloit, Illinois, United States [City]; population was 4,072 in 1990; housing units was 1,789 in 1990; location is 42°29'N 89°2'W; land area is 3.13 square miles (2,004 acres); water area is 0.10 square miles (62 acres); FIPS code is 70590 [SourceCBP]