31728 -- U.S. ZIP code Municipality (1990): CAIRO, Georgia All ZIPs for this municipality (1990): 31728 Population (2000): 18008 Housing Units (2000): 7532 Land area (2000): 216.563164 sq. miles (560.895997 sq. km) Water area (2000): 0.850924 sq. miles (2.203883 sq. km) Total area (2000): 217.414088 sq. miles (563.099880 sq. km) Located within: Georgia (GA) Location: 30.870390 N, 84.213438 W