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 now concurrent with Interstate 70 for a significant portion of its length from the Utah state line to Denver. Within the city limits, US 6 follows Denver's 6th Avenue (known as "6th Avenue Freeway"). The highway then travels north briefly, and it follows Interstate 76 for most of its length east of Denver. It is unsigned while it is overlapped. The highest altitude along US 6 is at Loveland Pass, where it crosses the Continental Divide. It continues down Clear Creek Valley until it reaches I-70, where it is briefly overlapped until I-70 leaves Clear Creek Valley. US 6 continues down Clear Creek and into Denver, where it turns into a freeway with six lanes. East of Denver, it continues east while joined with I-76 until it reaches Sterling, where it diverges from the interstate. The last town in Colorado that it passes is Holyoke.