South Plainfield, New Jersey, United States [Borough]; population was 20,489 in 1990; housing units was 6,823 in 1990; location is 40°35'N 74°25'W; land area is 8.36 square miles (5,350 acres); water area is 0.04 square miles (24 acres); FIPS code is 69390 [SourceCBP]