U.S. Route 23 (US 23) is a part of the U.S. Highway System that runs from Jacksonville, Florida to Mackinaw City, Michigan. In Tennessee, the U.S. Highway runs 57.5 miles (92.5 km) from the North Carolina state line, at Sam's Gap, north to the Virginia state line, in Kingsport. With a predominant concurrency with Interstate 26, US 23 is a divided four-lane freeway that follows Corridor B of the Appalachian Development Highway System and serves as a major thoroughfare in the Tri-Cities. The entire route of US 23 in Tennessee is an interstate grade freeway.