Interstate 80
I-80 is the Interstate Highway that most closely approximates the route of the historic Lincoln Highway, the first road across the United States. The highway roughly traces other historically significant travel routes in the Western United States: the Oregon Trail across Wyoming and Nebraska, the California Trail across most of Nevada and California, the first transcontinental airmail route, and except in the Great Salt Lake area, the entire route of the First Transcontinental Railroad. From near Chicago east to near Youngstown, Ohio, I-80 is a toll road, containing the majority of both the Indiana Toll Road and the Ohio Turnpike. I-80 runs concurrently with I-90 from near Portage, Indiana, to Elyria, Ohio. In Pennsylvania, I-80 is known as the Keystone Shortway, a non-tolled freeway that crosses rural north-central portions of the state on the way to New Jersey and New York City.
Route number
The U.S. Highway System, indicated by a white shield with black numbers, is based on a numbering grid, with odd routes running generally north–south and even routes running east–west. Primary routes have a one- or two-digit number, and are supplemented by spur routes that add a hundreds digit to their parent route. Routes increase from east-to-west and north-to-south, such that U.S. Route 1 follows the Atlantic Seaboard fall line, while U.S. Route 101 does the same at the Pacific Ocean Coast. Likewise U.S. Route 2 runs near the Canadian border, while U.S. Route 98 follows the Gulf Coast. Major cross-country routes end in either a "1" or a "0". For example, U.S. Route 20 is a route that runs over from Boston, Massachusetts, to Newport, Oregon, while U.S. Route 41 spans the country from Miami, Florida, to the Upper Peninsula of Michigan. Routes like U.S. Route 141 and U.S. Route 441 branch off U.S. Route 41. The now defunct U.S. Route 66, known as the "Mother Road", was a cultural touchstone that inspired literature, songs, and other media.