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.
U.S. Route 6
US 6 is a diagonal route, whose number is out of sequence with the rest of the U.S. Highway grid in the western US. When it was designated in 1926, US 6 only ran east of Erie, Pennsylvania. Subsequent extensions, largely replacing the former U.S. Route 32 (US 32) and U.S. Route 38 (US 38), have taken it south of US 30 near Chicago, Illinois, US 40 near Denver, Colorado (past the end of US 38), US 50 at Ely, Nevada, and even US 70 near Los Angeles, California, due to its north–south alignment in that state.