31558 -- U.S. ZIP code Municipality (1990): SAINT MARYS, Georgia All ZIPs for this municipality (1990): 31558 Population (2000): 20787 Housing Units (2000): 7323 Land area (2000): 97.764980 sq. miles (253.210124 sq. km) Water area (2000): 0.478547 sq. miles (1.239432 sq. km) Total area (2000): 98.243527 sq. miles (254.449556 sq. km) Located within: Georgia (GA) Location: 30.761081 N, 81.569120 W