Commonwealth Ave. in Boston.

where US20 Begins.

The end of Route 20.  Newport, Oregon.

US Route 20 is the longest road in the United States. It starts near Fenway Park in Boston and runs 3,365 miles to Newport, Oregon.  Route 20 crosses Massachusetts, New York, Pennsylvania, Ohio, Indiana, Illinois, Iowa, Nebraska, Wyoming, Montana, Idaho and Oregon.  Driving 20 brings home the diversity of the Untied States.  It is Commonwealth Ave. in Boston, Euclid Ave. in Cleveland and 95th Street in Chicago. It is also the Main Street of dozens of little towns. 

Route 20 runs through hundreds of miles of corn fields, and high desert and rises and falls through the Berkshire Mountains of Massachusetts and the Cascades of Oregon.  Route 20 also runs through Yellowstone Park.

Some of Route 20 is four-lane but not limited access.  Only about 32 miles of Route 20 are also Interstate 25 in Wyoming.