U.S. Route 231 (US 231) is a north-south U.S highway that is a parallel route of US 31. It runs for 912 miles (1,468 km) from St. John, Indiana, at US 41 to south of US 98 in downtown Panama City, Florida.One of its most notable landmarks is the William H. Natcher Bridge, a 0.853 miles (1.373 km) long cable-stayed bridge that connects Rockport, Indiana, to Owensboro, Kentucky, spanning the Ohio River.