Sacagawea's story is told against the backdrop of the Lewis and Clark Expedition of 1804. Instigated by President Thomas Jefferson' s interest in the country west of the Mississippi River, the expedition was led by Captain Meriweather Lewis and Lieutenant William Clark, both familiar with the hardships of frontier life and the threat of Indian warfare. The expedition explored American territory newly acquired from France in the 1803 Louisiana Purchase.

On May 14, 1804, the expedition, consisting of Lewis and Clark; Clark's servant York; fourteen soldiers; nine Kentuckians; and two French boatmen started up the Missouri River. In July they had their first encounter with Native Americans, a peaceful one, and in October they reached the camps of the Mandan tribe, near present-day Stanton, North Dakota. There they built a fortified camp, Fort Mandan, and spent the winter. At this point Lewis and Clark hired Charbonneau and his Shoshone wife, the invaluable...