US 14 ALT north to SR294, 294 to SR120. 120 changes to SR72 at the Montana state line. Stay on SR72 until it meets US310 at Bridger. 310 meets US212 at Rockvale, MT. Then it's not far on US212 until you hit I-90 at Laurel, MT. That's if you are going north or west.
If you are headed east or south...take US 14 east to Greybull. Go south on US20 to Worland and then pick up US 16 over to Buffalo, pick up I-90 at Buffalo. US 16 is the easiest pull across the Big Horns, but not the most scenic.
Single empty-nester in Middle TN, sometimes with a friend or grandchild on board