61071 -- U.S. ZIP code Municipality (1990): ROCK FALLS, Illinois All ZIPs for this municipality (1990): 61071 Population (2000): 14862 Housing Units (2000): 6256 Land area (2000): 73.849584 sq. miles (191.269536 sq. km) Water area (2000): 0.976155 sq. miles (2.528230 sq. km) Total area (2000): 74.825739 sq. miles (193.797766 sq. km) Located within: Illinois (IL) Location: 41.759473 N, 89.694527 W