In Alabama and Tennessee, all of the U.S. Highways in each state have one or more unsigned state highways designated along its length. US 43 travels concurrently with Alabama State Route 13 (SR 13) from its southern terminus to an intersection in southeastern Fayette County. For the rest of its length in the state, US 43 is concurrent with signed state highways. In Tennessee, US 43 travels concurrently with Tennessee State Route 6 (SR 6) along its entire length in the state. It also has an unsigned concurrency with SR 227 between Saint Joseph and Loretto.