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.
Alaska
Alaska has few road connections compared to the rest of the U.S. The state's road system covers a relatively small area of the state, linking the central population centers and the Alaska Highway, the principal route out of the state through Canada. The state capital, Juneau, is not accessible by road, only a car ferry, which has spurred several debates over the decades about moving the capital to a city on the road system, or building a road connection from Haines. The western part of Alaska has no road system connecting the communities with the rest of Alaska.
The Interstate Highways in Alaska consists of a total of 1082 miles. One unique feature of the Alaska Highway system is the Anton Anderson Memorial Tunnel, an active Alaska Railroad tunnel recently upgraded to provide a paved roadway link with the isolated community of Whittier on Prince William Sound to the Seward Highway about southeast of Anchorage at Portage. At , the tunnel was the longest road tunnel in North America until 2007. The tunnel is the longest combination road and rail tunnel in North America.