Map of possible topographic barriers that would allow expansion of bison outside of Yellowstone Park to range freely on public lands (mostly). These are areas where livestock have already been pretty much removed.

 

 

Note that the red bars represent the barrier locations.

I drew in the boundaries of Yellowstone Park in green. This is just the NW corner of the Park, but that is the relevant corner. Bison rarely leave from other parts of the Park.

 

Yellowstone proposed bison boundaries