A small portion of U.S. 431 is famous for a unique reason. U.S. 431 crosses the Green River in McLean County, Kentucky. It is at that crossing in the city of Livermore that U.S. 431 crosses two rivers and also crosses into Ohio County before completing the river crossing back in McLean County. This is the only known crossing of this type in the United States: a road starts in one county, crosses two separate rivers, crosses a sliver of land within another county, and then terminates the bridge crossing in the original county it started in. This special feature is marked by a state historical marker on both approach ends of the bridge.