Dr. Gary Moulton is the keynote speaker for the Encounters on the Prairie Chapter of the Lewis and Clark Trail Heritage Foundation's regional meeting and symposium celebrating the life of Sacagawea.  The meetings are September 28-30 in Ft. Pierre.  Moulton is Thomas C. Sorensen Professor Emeritus of History at the University of Nebraska-Lincoln.  He's known for his work as editor of the award-winning Journals of the Lewis and Clark Expedition.  This December marks the 200th anniversary of Sacagawea's reported death in present day South Dakota.