61841 -- U.S. ZIP code Municipality (1990): FAIRMOUNT, Illinois All ZIPs for this municipality (1990): 61841 Population (2000): 1352 Housing Units (2000): 560 Land area (2000): 58.149322 sq. miles (150.606046 sq. km) Water area (2000): 0.277068 sq. miles (0.717603 sq. km) Total area (2000): 58.426390 sq. miles (151.323649 sq. km) Located within: Illinois (IL) Location: 40.039632 N, 87.830527 W