Jefferson’s Corps of Discovery Heads West

To head the expedition into the Louisiana territory, Jefferson appointed his friend and personal secretary, twenty-nine-year-old army captain Meriwether Lewis, who was instructed to form a Corps of Discovery. Lewis in turn selected William Clark, who had once been his commanding officer, to help him lead the group.

Figure 2. Charles Willson Peale, celebrated portraitist of the American Revolution, painted both William Clark (a) and Meriwether Lewis (b) in 1810 and 1807, respectively, after they returned from their expedition west.

Jefferson wanted to improve the ability of American merchants to access the ports of China. Establishing a river route from the Mississippi River to the Pacific Ocean, the fabled Northwest Passage, was crucial to capturing a portion of the fur trade that had proven so profitable to Great Britain. He also wanted to legitimize American claims to the land against rivals, such as Great Britain and Spain. Lewis and Clark were thus instructed to map the territory through which they would pass and to explore all tributaries of the Missouri River. This part of the expedition struck fear into Spanish officials, who believed that Lewis and Clark would encroach on New Mexico, the northern part of New Spain. Spain dispatched four unsuccessful expeditions from Santa Fe to intercept the explorers. Lewis and Clark also had directives to establish friendly relationships with the western tribes, introducing them to American trade goods and encouraging warring groups to make peace. Establishing an overland route to the Pacific would bolster U.S. claims to the Pacific Northwest, first established in 1792 when Captain Robert Gray sailed his ship Columbia into the mouth of the river that now bears his vessel’s name and forms the present-day border between Oregon and Washington. Finally, Jefferson, who had a keen interest in science and nature, ordered Lewis and Clark to take extensive notes on the geography, plant life, animals, and natural resources of the region into which they would journey.

After spending the winter of 1803–1804 encamped at the mouth of the Missouri River while the men prepared for their expedition, the corps set off in May 1804. Although the thirty-three frontiersmen, boatmen, and hunters took with them Alexander Mackenzie’s account of his explorations and the best maps they could find, they did not have any real understanding of the difficulties they would face. Fierce storms left them drenched and freezing. Enormous clouds of gnats and mosquitos swarmed about their heads as they made their way up the Missouri River. Along the way they encountered (and killed) a variety of animals including elk, buffalo, and grizzly bears. One member of the expedition survived a rattlesnake bite. As the men collected minerals and specimens of plants and animals, the overly curious Lewis sampled minerals by tasting them and became seriously ill at one point. What they did not collect, they sketched and documented in the journals they kept. They also noted the customs of the Indian tribes who controlled the land and attempted to establish peaceful relationships with them in order to ensure that future White settlement would not be impeded.

The corps spent their first winter in the wilderness, 1804–1805, in a Mandan village in what is now North Dakota. There they encountered a reminder of France’s former vast North American empire when they met a French fur trapper named Toussaint Charbonneau. When the corps left in the spring of 1805, Charbonneau accompanied them as a guide and interpreter, bringing his teenage Shoshone wife, Sacagawea, and their newborn son. Charbonneau knew the land better than the Americans, and Sacagawea proved invaluable in many ways, not least of which was that the presence of a young woman and her infant convinced many groups that the men were not a war party and meant no harm.

Figure 3. In this idealized image, Sacagawea leads Lewis and Clark through the Montana wilderness. In reality, she was still a teenager at the time and served as interpreter; she did not actually guide the party, although legend says she did. Kidnapped as a child, she would not likely have retained detailed memories about the place where she grew up.

The corps set about making friends with Native tribes while simultaneously attempting to assert American power over the territory. Hoping to overawe the people of the land, Lewis would let out a blast of his air rifle, a relatively new piece of technology the Indians had never seen. The corps also followed Native custom by distributing gifts, including shirts, ribbons, and kettles, as a sign of goodwill. The explorers presented Native leaders with medallions, many of which bore Jefferson’s image, and invited them to visit their new “ruler” in the East. These medallions or peace medals were meant to allow future explorers to identify friendly Native groups. Not all efforts to assert U.S. control went peacefully; some Indians rejected the explorers’ intrusion onto their land. An encounter with the Blackfoot turned hostile, for example, and members of the corps killed two Blackfoot men.

After spending eighteen long months on the trail and nearly starving to death in the Bitterroot Mountains of Montana, the Corps of Discovery finally reached the Pacific Ocean in 1805 and spent the winter of 1805–1806 in Oregon. They returned to St. Louis later in 1806 having lost only one man, who had died of appendicitis. Upon their return, Meriwether Lewis was named governor of the Louisiana Territory. Unfortunately, he died only three years later in circumstances that are still disputed, and before he could write a complete account of what the expedition had discovered.

Although the Corps of Discovery failed to find an all-water route to the Pacific Ocean (for none existed), it nevertheless accomplished many of the goals Jefferson had set. The men traveled across the North American continent and established relationships with many Indian tribes, paving the way for fur traders like John Jacob Astor who later established trading posts solidifying U.S. claims to Oregon. Delegates of several tribes did go to Washington to meet the president. Hundreds of plant and animal specimens were collected, several of which were named for Lewis and Clark in recognition of their efforts. And the territory was now more accurately mapped and legally claimed by the United States. Nonetheless, most of the vast territory, home to a variety of Native peoples, remained unknown to Americans.