Underwood, IA -- U.S. city in Iowa Population (2000): 688 Housing Units (2000): 266 Land area (2000): 0.364638 sq. miles (0.944409 sq. km) Water area (2000): 0.000000 sq. miles (0.000000 sq. km) Total area (2000): 0.364638 sq. miles (0.944409 sq. km) FIPS code: 79500 Located within: Iowa (IA), FIPS 19 Location: 41.386944 N, 95.678584 W ZIP Codes (1990): 51576 Note: some ZIP codes may be omitted esp. for suburbs. Headwords: Underwood, IA Underwood