CansasKamper wrote:
...I heard the Big Horn mountains can be steep. Any particular route through there or through the Black Hills?...
Where are you staying in Yellowstone? From West Yellowstone, US-191 will take you to I-90 without any serious mountain driving. Us-89 will take you from the North entrance of the park to I-90 without any serious mountain driving. If you are going out the East entrance to visit Cody, WY-120, MT-72, US-310 will take you to I-90 without any serious mountain driving. US-16 is the more scenic route, but does have grades in the 6-7% range.
If you do not take US-16, I-90 will take you close to the
Little Bighorn Battlefield which if you have the time is worth a visit in my opinion. As is
Devils Tower.