Another good route would be going back & forth across Glacier National Park. You could start from Whitefish head over to West Glacier, ride across the park to St. Mary's, and then maybe go up to the Many Glacier area and then do the route in reverse on the way back. You won't find more spectacular scenery anywhere else. Also it's best to ride across Glacier after Labor Day since before then you have to reach the top of Logan Pass by 11am, after Labor Day there's no time limit.