33813 -- U.S. ZIP code Municipality (1990): SOUTHSIDE, Florida All ZIPs for this municipality (1990): 33811 33813 Population (2000): 35411 Housing Units (2000): 13566 Land area (2000): 40.821998 sq. miles (105.728486 sq. km) Water area (2000): 1.359972 sq. miles (3.522312 sq. km) Total area (2000): 42.181970 sq. miles (109.250798 sq. km) Located within: Florida (FL) Location: 27.965469 N, 81.922154 W