31780 -- U.S. ZIP code Municipality (1990): PLAINS, Georgia All ZIPs for this municipality (1990): 31780 Population (2000): 2313 Housing Units (2000): 941 Land area (2000): 77.170377 sq. miles (199.870351 sq. km) Water area (2000): 0.183923 sq. miles (0.476359 sq. km) Total area (2000): 77.354300 sq. miles (200.346710 sq. km) Located within: Georgia (GA) Location: 32.026125 N, 84.393615 W