We are in the process of planning a road trip from Portland with hopes of seeing Mt. Rushmore and surrounding areas in SD, Yellowstone, Grand Tetons, and Glacier. We have a good amount of time, close to 3 weeks. More if needed. We are thinking that due to a reservation at Old Faithful Inn, middle of our time, we would go towards SD first via Coeur D' Alene, then head to Grand Tetons and Yellowstone via Nebraska. Then finally hit Glacier on the way home. My question is how many days are needed for each of these areas and is there anything that is a must see that we might not have though of?