US 129 begins at US 19/US 27 Alternate/US 98 in Chiefland, Florida, along hidden SR 47 until it reaches SR 26 in Trenton. From there, the road is signed along hidden SR 49. It then moves west, briefly overlapping US 27 and heads north again in Branford, before that road intersects SR 349, which used to also serve as US 129 Alternate. From here, it intersects with US 90/SR 51 in Live Oak, taking SR 51 as the new hidden state road, then meets I-10 at exit 283, and later I-75 at exit 451. During a concurrency with US 41 in Jasper, US 129 loses SR 51 as a hidden route after the concurrency ends and runs northwest along SR 100 into Georgia.
Georgia
US 129 provides the primary route between central Georgia and Athens. It approaches Athens from the south where it joins SR 10 Loop, a mostly interstate-grade bypass that rings Athens-Clarke County. Here US 129 turns right, toward the northeast, where it runs concurrently with US 78/US 29/US 441/SR 15 along the bypass. US 129 intersects with US 29 northeast of Athens and continues along SR 10 Loop westward before exiting at Jefferson Road where it winds northwesterly towards Gainesville as one of several routes to I-85 from Athens.
North Carolina
From the Georgia state line, it travels northeast to Topton, where it goes north to Robbinsville followed by Tennessee, through Deals Gap.
Tennessee
US 129 enters Tennessee to the west of Great Smoky Mountains National Park and rides along Chilhowee Lake for a short distance before turning due north. In this stretch after the Tennessee–North Carolina state line, drivers will encounter 318 curves in a distance of around 11 miles. These curves make this stretch of highway a well-known motorcycle/sports car destination named Tail Of The Dragon. On weekends, through spring to the fall months, visitors are likely to see numerous riders and drivers on this stretch of the highway to experience the thrill and scenery. US 129 then travels due north, becoming known as Alcoa Highway and passing through the city ofMaryville. It travels through Alcoa, passing by McGhee Tyson Airport, and then intersecting I-140. US 129 then crosses the Tennessee River on the James E. "Buck" Karnes Bridge into Knoxville. Shortly thereafter, US 129 becomes a limited-access highway for a short distance. It has an interchange with US 11/US 70 immediately after entering Knoxville. Shortly thereafter, US 129 meets its northern terminus, an interchange with I-40.
U.S. 129 is mentioned in the popular country song Bottoms Up by Brantley Gilbert: "I see you and me riding like Bonnie and Clyde, Goin 95 burning down 129." U.S. 129 is known particularly for being a route containing hundreds of mountainous curves and turns. With the rise of the internet and telecommunications, the Tennessee section of the route has become popularized by its motoring enthusiasts who share their experiences through social messaging boards and media outlets. This small stretch of around 11 miles starting at Deals Gap just before the Tennessee state line in North Carolina, has been nicknamed Tail Of The Dragon.
