61436 -- U.S. ZIP code Municipality (1990): GILSON, Illinois All ZIPs for this municipality (1990): 61436 Population (2000): 1021 Housing Units (2000): 411 Land area (2000): 64.363241 sq. miles (166.700021 sq. km) Water area (2000): 0.015457 sq. miles (0.040033 sq. km) Total area (2000): 64.378698 sq. miles (166.740054 sq. km) Located within: Illinois (IL) Location: 40.859964 N, 90.222124 W