Lewis and Clark’s Corps of Discovery left its headquarters, north of St. Louis, on May 14, 1804. Two hundred years ago this March, the explorers were wintering in North Dakota, awaiting better weather before attempting the Rockies. By then the company included the Shoshone interpreter Sacagawea and her newborn son, Jean Baptiste. Traveling sometimes by water, sometimes on foot and horseback, the expedition reached the Washington coast in November 1805 and returned to St. Louis on September 23, 1806.