Milwaukee WI to West Yellowstone MT

[Lifemagician]

The shortest route would be to leave Yellowstone via US-14 east (the Bighorn Scenic Highway)to join I-90 at Ranchester WY.

At Cody you could divert onto Alt 14, which is an incredibly scenic route through Lovell, past Big Horn Canyon and a short walk to the Medicine Wheel... picking up I-90, as above.

Lifey