63401 -- U.S. ZIP code Municipality (1990): HANNIBAL, Missouri All ZIPs for this municipality (1990): 63401 Population (2000): 21891 Housing Units (2000): 9628 Land area (2000): 113.622461 sq. miles (294.280811 sq. km) Water area (2000): 0.156778 sq. miles (0.406053 sq. km) Total area (2000): 113.779239 sq. miles (294.686864 sq. km) Located within: Missouri (MO) Location: 39.695798 N, 91.400846 W