61920 -- U.S. ZIP code Municipality (1990): CHARLESTON, Illinois All ZIPs for this municipality (1990): 61920 Population (2000): 24572 Housing Units (2000): 9618 Land area (2000): 148.863826 sq. miles (385.555522 sq. km) Water area (2000): 0.641117 sq. miles (1.660485 sq. km) Total area (2000): 149.504943 sq. miles (387.216007 sq. km) Located within: Illinois (IL) Location: 39.496547 N, 88.173485 W