The Pan-American Highway
For sheer distance you can’t beat the Pan-American Highway linking PrudhoeBay, Alaska with Ushuaia in the far south of Argentina on an epic 29,800-mile (48,000-km) route.
Purists may argue that the Pan-American doesn’t qualify as a single highway, since on the North American side it’s a network of roads that use different names -but this is still apretty impressive route.
The Pan-American road signs start on the Mexican border and the road snakes down through Panama before coming to an abrupt holt at the Darien Gap. This 54 mole (87 km) stretch of rainforest on the Panama/Columbia frontier is notorious for smugglers, making it impassible for all but the most foolhardy adventurers.
You can pick the Highway up again on the Columbian side then it hugs the Pacific Coast, working down through Ecuador, Peru, and Chile before crossing over to Buenos Aires for the final stretch through Patagonia and Tierra del fuego.