61401 -- U.S. ZIP code Municipality (1990): GALESBURG, Illinois All ZIPs for this municipality (1990): 61401 Population (2000): 36568 Housing Units (2000): 15436 Land area (2000): 116.791237 sq. miles (302.487902 sq. km) Water area (2000): 0.529145 sq. miles (1.370479 sq. km) Total area (2000): 117.320382 sq. miles (303.858381 sq. km) Located within: Illinois (IL) Location: 40.948073 N, 90.368715 W