Jean Baptiste Charbonneau (February 11, 1805 – May 16, 1866) was an American explorer who is best known for traveling across North America as an infant with his mother Sacagawea as part of the Lewis and Clark Expedition.

You can read more about his interesting life and how he came to rest at this place here:
http://en.wikipedia.org/wiki/Jean_Baptiste_Charbonneau

Curious about this grave is that it is covered with loose coins that should have stolen or been blown away by the wind long ago. He is honored by his Indian brethren with pealed corn husks and delicate, beaded grave marker.
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