U.S. Route 20
U.S. Highway 20 (US 20) is an east–west United States highway that stretches from the Pacific Northwest all the way to New England. The "0" in its route number indicates that US 20 is a coast-to-coast route. Spanning , it is the longest road in the United States, and particularly from Newport, Oregon to Boston, Massachusetts, the route is roughly parallel to that of the newer Interstate 90 (I-90), which is in turn the longest Interstate Highway in the U.S. There is a discontinuity in the official designation of US 20 through Yellowstone National Park, with unnumbered roads used to traverse the park.
Transportation in Appalachia
The next great leap in transportation was the creation of the U.S. Highway system in 1926, replacing the auto trails. The longest primary US highway contained in Appalachia is US 11 traversing the eastern side. US 21 was another primary US highway, but much of its route has been decommissioned and replaced with Interstate 77. These make/made up the north-south routes. East-west routes include US 30, US 33, US 40, US 50, US 60, and US 70. Many spur routes such as US 220 and US 119 serve various parts of Appalachia.