Other notable features in Montana are the glaciated country in the north, from Glacier International Park in the west to the windswept plains in the east, and the great Precambrian Belt complex in the Rockies.
Buy a paper copy of this map from Montana State University. It has more material than I've shown here. The state's Bureau of Mines and Geology published an updated state geologic map in 2007, about 1-1/2 by 2 meters in size. It costs considerably more but has infinitely more information.
More Montana resources on About.com:
Montana Geography, State Symbols & Facts
Montana National Parks
Montana State Parks for Spring
Montana State Parks for Winter
Montana Scenic Roads
Montana Resorts & Guest Ranches
Montana Bed & Breakfasts