The Yellowstone River Was the Route of the Pioneers.

…. "[Now we follow the Yellowstone Valley right across Montana.]"

After Gravel Road, Along North Side of Yellowstone River From Miles City => /\ Above /\ Photo Shows => Yellowstone River Crossing Back to I-94, Forsythe, MT.
….As any alert land traveler (and history buff) soon discovers, river valleys generally provide an easier passage for nearly all modes of land travel as well as road construction.
….Rivers and streams often allow boat navigation and sometimes the first ways into and through a new territory. These facts were important for early explorers and settlers. Additionally valleys, compared to the surrounding terrain, are more favorable to agriculture. For these reasons roads and then towns become established in valleys such as the Yellowstone Valley.
…. All along, The Narrator’s goal has been Bozeman, MT. Thus after entering Montana, (and according to above conclusions), it should not be surprising that the ZMM Route follows for 160 miles fairly close to a river, the Yellowstone.
….It is thus, also not surprising that this river was also traveled by Captain Merriwether Clark….. So both the Narrator and Lewis and Clark traveled West through this area of Montana, for the same reason.
… Basically the facts of geography, given above, lead/constrained the ZMM Route so that it repeatedly encounters Lewis and Clark Landmarks, as you will see in forthcoming photos.

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(Photo = Summer2006 0317 ...... ZMM Page = 92 ...... WayPt = 104m)