U.S. Route 51 is a south-north United States highway that runs for 1,286 miles (2,070 km) from the western suburbs of New Orleans, Louisiana to within 100 feet (30 m) of the Wisconsin–Michigan border. Much of the highway in Illinois and southern Wisconsin runs parallel to or overlaps Interstate 39 (I-39), and much of the route in several states also parallels the Illinois Central Railroad.