What is a river?
The Upper Mississippi is a series of lakes with railroads on both banks.
The Lower Mississippi has been dramatically channelized.
The Missouri south of Sioux City is free-flowing, but hard to get close to.
Above Yankton it is a series of massive reservoirs that have drowned the riparian environment.
The Missouri at Missouri Breaks is free-flowing, but roadless.
From Wolf Creek to Great Falls, Recreation Road generally follows the river.
The Yellowstone is the longest free-flowing river in the Lower 48.
The valley has a major interstate and a transcontinental railroad.
But, long stretches of Old US 10 are there for the taking.
Totally empty road with significant river stretches - cliffs, eagles, hawks.
And September is a magnificent month to do it.
Takes some planning.