Riva, MD -- U.S. Census Designated Place in Maryland Population (2000): 3966 Housing Units (2000): 1453 Land area (2000): 2.495849 sq. miles (6.464219 sq. km) Water area (2000): 0.406736 sq. miles (1.053441 sq. km) Total area (2000): 2.902585 sq. miles (7.517660 sq. km) FIPS code: 66400 Located within: Maryland (MD), FIPS 24 Location: 38.952079 N, 76.582135 W ZIP Codes (1990): 21140 Note: some ZIP codes may be omitted esp. for suburbs. Headwords: Riva, MD Riva