Lewis and Clark never had it so good: The exploring duo traversed these visually breathtaking landscapes without the benefit of internal combustion-aided transportation, making this highway that connects to the Lolo Pass in Montana all the more remarkable for us modern folk. Though remote in parts, Route 12's path through Idaho is particularly scenic, slicing through untrammeled creeks and forests for much of its circuitous path. Bring an audio book or a good conversationalist, but also be sure to lower the windows and listen to the great outdoors; it doesn't get more natural than this.