U.S. Route 31 (US 31) is a part of the United States Numbered Highway System that runs from Spanish Fort, Alabama, to the Mackinaw City, Michigan. In the U.S. state of Indiana, it is a State Road that enters the state via the George Rogers Clark Memorial Bridge between Louisville, Kentucky, and Clarksville, Indiana. The 266.02 miles (428.12 km) of US 31 that lie within Indiana serve as a major conduit. Some of the highway is listed on the National Highway System. Various sections are rural two-lane highway and urbanized four-lane divided expressway. The northernmost community along the highway is South Bend near the Michigan state line.