The US Geological Survey has a neat little site that let’s you see Lewis & Clark’s journey from a satellite view.

Each satellite view has some information about that particular leg of the expedition.  For instance image #14 tells us this:

Image Name: Camp Fortunate, Montana
August 17, 1805 

Image Source: Landsat 7 and DEM

Image Date:October 7, 2002

Image Description: Lewis and Clark were reunited at
this site after parting company near the Big Hole and Jefferson Rivers.
Lewis arrived first and lodged with a band of Shoshone. When the
Indians began preparing to head east to their buffalo hunting grounds,
Lewis persuaded them to wait for Clark’s return. When at last Clark
arrived with Sacagawea, she recognized the leader of the Shoshone as
her brother. It was in part this fortunate twist of fate that led to
the Shoshone agreeing to help the expedition cross the Continental
Divide—and gave the camp its name.

Digital TIFF File Size:Approx 160 MB

This is the kind of stuff that makes me shake my head in wonder at what information technology hath wrought on our world.