U.S. Route 129 is a spur of U.S. Route 29. It currently runs for 582 miles (937 km) from Knoxville, Tennessee to Chiefland, Florida at U.S. Route 19 and U.S. Route 98. It passes through the states of Tennessee, North Carolina, Georgia and Florida. It goes through the cities of Knoxville, Tennessee, Gainesville, Georgia, Athens, Georgia, and Macon, Georgia. Eleven miles of US 129 located on the Tennessee/North Carolina border is known as the Tail of the Dragon, a popular motorcycle and sports car destination. The name is apparently derived from the roadway's resemblance to a dragon's back. The segment runs from Tab Cat Creek to Deals Gap and has 318 curves.
U.S. 129 begins at US 19-Alternate US 27-US 98 in Chiefland, Florida along hidden SR 47 until it reaches Florida State Road 26 in Trenton. From there, the road is signed along Hidden SR 49. It then moves west, briefly overlapping U.S. Route 27(Hidden SR 20) and heads north again in Branford, before that road intersects Florida State Road 349, which used to double as U.S. Route 129 Alternate. From here it intersects with U.S. Route 90 and Florida State Road 51 in Live Oak, taking SR 51 as the new hidden State Road, then meets Interstate 10 at Exit 283, and later Interstate 75 at Exit 451. During a concurrency with U.S. Route 41 in Jasper, U.S. 129 loses SR 51 as a hidden route then after the concurrency ends runs noorthwest along hidden SR 100 into Georgia.