Diagonal, IA -- U.S. city in Iowa Population (2000): 312 Housing Units (2000): 154 Land area (2000): 0.908254 sq. miles (2.352367 sq. km) Water area (2000): 0.000000 sq. miles (0.000000 sq. km) Total area (2000): 0.908254 sq. miles (2.352367 sq. km) FIPS code: 21270 Located within: Iowa (IA), FIPS 19 Location: 40.808819 N, 94.341510 W ZIP Codes (1990): 50845 Note: some ZIP codes may be omitted esp. for suburbs. Headwords: Diagonal, IA Diagonal