The Lewis and Clark Expedition is a neat Google Maps “mashup” that shows the route of their journey. If you click on each “pushpin” you’ll see a photo, a brief explanation of what they were doing there, and an excerpt from their journal. You’re automatically advanced to the next point.
I’ll be adding it to both the United States History page on my website and to my United States History class blog.
Thanks to Google Maps Mania for the tip.