Start at mile zero on each end.
Historic Route 20 is the longest federal highway in the United States. It stretches across twelve states and has its ends at Boston, MA and Newport, OR.
The 3,365 miles was determined back in 1989. This number also included alternate alignments and older alignments now bypassed.
Route 20's designation has an eastern and western component as it is not signed through Yellowstone National Park.
