Johnston, IA -- U.S. city in Iowa Population (2000): 8649 Housing Units (2000): 3406 Land area (2000): 14.348360 sq. miles (37.162081 sq. km) Water area (2000): 1.141105 sq. miles (2.955447 sq. km) Total area (2000): 15.489465 sq. miles (40.117528 sq. km) FIPS code: 39765 Located within: Iowa (IA), FIPS 19 Location: 41.671337 N, 93.705800 W ZIP Codes (1990): 50131 Note: some ZIP codes may be omitted esp. for suburbs. Headwords: Johnston, IA Johnston