"If the expedition was just about a grand trip across the West, as great as that would be, it wouldn't capture my attention, or the attention of so many Americans," says Gary Moulton. his is professor of history at the University of Nebraska and teh editor of the 13-volume Journals of Lewis and Clark.
Lewis and Clark braved the unknown waters of the Missouri to chart America's future. As we approach the 200th anniversary of their sojourn, TIME reflects upon their sacrifice and achievement