Middletown, IA -- U.S. city in Iowa Population (2000): 535 Housing Units (2000): 223 Land area (2000): 0.611306 sq. miles (1.583276 sq. km) Water area (2000): 0.000000 sq. miles (0.000000 sq. km) Total area (2000): 0.611306 sq. miles (1.583276 sq. km) FIPS code: 51735 Located within: Iowa (IA), FIPS 19 Location: 40.827925 N, 91.260347 W ZIP Codes (1990): 52638 Note: some ZIP codes may be omitted esp. for suburbs. Headwords: Middletown, IA Middletown