Found this site of a guy who travels around by foot with three mules, seemed like an interesting idea:

“… a most first necessary step is an interstate trail system in this country going in all four directions — north, south, east and west — linking all states to all other states passed and funded by Congress with the same energy and effort that was applied to the building of the interstate freeway system, which was built for the exclusive use of automobiles. Cyclists, pedestrians, equestrians, people in wheelchairs, etc. are being removed from this public throughfare simply becuase there is no room by which to use it alongside motorists.”