62521 -- U.S. ZIP code Municipality (1990): DECATUR, Illinois All ZIPs for this municipality (1990): 62521 62522 62523 Population (2000): 37281 Housing Units (2000): 16368 Land area (2000): 66.369553 sq. miles (171.896345 sq. km) Water area (2000): 0.026734 sq. miles (0.069242 sq. km) Total area (2000): 66.396287 sq. miles (171.965587 sq. km) Located within: Illinois (IL) Location: 39.828586 N, 88.929075 W