Arnold, MO -- U.S. city in Missouri Population (2000): 19965 Housing Units (2000): 7913 Land area (2000): 11.248180 sq. miles (29.132651 sq. km) Water area (2000): 0.333948 sq. miles (0.864922 sq. km) Total area (2000): 11.582128 sq. miles (29.997573 sq. km) FIPS code: 01972 Located within: Missouri (MO), FIPS 29 Location: 38.432753 N, 90.369393 W ZIP Codes (1990): 63010 Note: some ZIP codes may be omitted esp. for suburbs. Headwords: Arnold, MO Arnold