The Lewis and Clark Expedition

Written by: Edward G. Lengel, The National World War II Museum

Thomas Jefferson became president in 1801 determined to introduce a new vision of the future of the United States. Suspicious of centralized government, standing armies, and what he considered to be the ostentatious political formalities espoused by Washington and Adams, Jefferson hoped to turn the nation’s energies inward toward peaceful expansion into the North American continent by virtuous small farmers. Jefferson imagined the United States as an agrarian nation that would become the world’s bread basket. He also envisioned American waterways as a means of spreading settlement, commerce, and republican ideas into the interior.

This preoccupation with westward expansion via interior waterways was not new. George Washington had eagerly explored Potomac River navigation as a means of simultaneously opening up the interior to settlement and uniting the nation (including whites and Native Americans) in the common bonds of commerce. Eighteenth- and early nineteenth- century American business owners invested heavily in land companies that sought to purchase and settle territory in the Ohio and Mississippi regions, for example, and hoped to link them with eastern settlements along major waterways. Jefferson, concerned about his seemingly perpetual and growing personal debts, invested in some of these schemes too. Unlike most of his contemporaries, however, he added an intellectual dimension to expansionism: As an amateur scientist and anthropologist, he avidly sought to learn the natural history of North America and the history and culture of its native inhabitants.

Other issues intervened, though, before Jefferson could pursue this course wholeheartedly. The election of 1800 had been close, and bitter tensions between groups roughly termed Republican and Federalist (or Jeffersonian and Hamiltonian) persisted. At the core of these tensions lay differences over their views of the French Revolution, which had begun in 1789 and subsequently radicalized under the Reign of Terror. French political radicalism had subsided somewhat by 1801, but France was rapidly falling under the sway of one of the most brilliant military leaders of all time: Napoleon Bonaparte. Though Jefferson and his allies admired French republicanism and culture, the authoritarian Napoleon stood as the antithesis of everything they believed in politically. Even so, staying neutral in the growing world conflict between Great Britain and France and their respective allies looked next to impossible, especially with both sides warring on U.S. commerce.

A turning point in the global conflict came not in Europe but in North America, with the culmination of the Haitian Revolution. A 1791 revolt of African slaves on the French Caribbean island of Saint-Domingue had led to a declaration of independence and establishment of a constitution by revolutionary leader Toussaint Louverture in 1801. Napoleon initially hoped to restore French rule on the island as a step toward recovering the French North American empire, which, from 1800, had included the Louisiana Territory once held by Spain. The army he sent to Saint-Domingue in 1802, however, quickly succumbed to yellow fever and insurrection, which wiped out what the French leader had intended as an instrument for expanding his influence throughout the western hemisphere. With his American plans in ruins and military pressures growing in Europe, Napoleon rapidly lost interest in the once-tantalizing Louisiana Territory.

Recognizing the strategic importance of the Louisiana Territory to the future of the United States, Jefferson dispatched former Minister to France James Monroe to join current Minister Robert Livingston in Paris. He instructed them to negotiate with Napoleon’s government for the acquisition of West Florida and New Orleans, for a maximum of $10 million. The French leader stunned Livingston and Monroe by offering to sell the entire Louisiana Territory (828,000 square miles of land) for $15 million. The two men exceeded their authority by agreeing in effect to purchase the territory. The treaty was signed in Paris on May 2, 1803.

Jefferson, although troubled by the question whether the treaty was constitutional, secured its passage through the Senate that autumn. It went into effect in December, effectively doubling the size of the United States. The purchase helped preserve the American desire for neutrality, because it helped rid part of the frontier of a significant European power. It also decreased the concern that settlers would join with foreign powers and imperil the American Union.

This map shows the territory added to the United States in the Louisiana Purchase of 1803. The purchase nearly doubled the size of the United States, adding territory from the Mississippi River to the Rocky Mountains. (attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license)

The Louisiana Territory had been claimed by a succession of European imperial powers but had never been extensively explored. Native American tribes had lived in the region for thousands of years, but they only intermittently communicated and traded with Europeans. Jefferson possessed limited information about them. He was particularly intrigued by the possibility that North America might be navigable from the Mississippi River to the Pacific Ocean via the Missouri and Columbia Rivers, opening up boundless possibilities for American trade and influence. With this in mind, he decided to assemble and dispatch an exploratory expedition.

Jefferson’s choice for leader of the expedition was Meriwether Lewis, who was born in 1774 near Charlottesville, Virginia, and had become the president’s private secretary. Well-educated, fit, and a politically reliable Republican, Lewis shared Jefferson’s passion for exploration. He, in turn, chose fellow Virginian and seasoned frontiersman William Clark as the expedition’s co-commander. The expedition, later to be known as the Corps of Discovery, departed Camp Dubois on the Mississippi River near St. Louis on May 14, 1804. Led by Lewis and Clark, it included more than forty individuals.

Although the expedition was exploratory, with a mandate to gather scientific and anthropological knowledge and, above all, to map potential water routes to the west, it was also officially military in character and organization. Lewis and Clark were charged with conveying the transfer of sovereignty in the region: If they encountered any Native Americans and Europeans along their travels, it was Lewis and Clark’s responsibility to tell such groups they were now residing in the United States. In this, the explorers were fortunate to encounter the Shoshone Indian Sacagawea and her French-Canadian husband Toussaint Charbonneau, who joined the expedition and served as interpreters.

(a) This detail from a mural in the Montana House of Representatives depicts Lewis and Clark alongside Sacagawea at Three Forks. (b) Meriwether Lewis and (c) William Clark were both painted by Charles Wilson Peale c. 1810, but no known portraits of Sacagawea exist.

The Lewis and Clark expedition’s journey across the Continental Divide and the Rocky Mountains to the Pacific Ocean, which the party reached in November 1805, has become an American legend. Fortunately for posterity, Lewis and other participants kept careful journals of the expedition’s progress, and Clark prepared valuable (if not always accurate) maps. Although they did not succeed in discovering Jefferson’s long-cherished water route to the Pacific(a quest that would continue for many decades) Lewis and Clark symbolically fostered the concept of the nation’s potential expansion across the entire North American continent.

Lewis and Clark returned to St. Louis in September 1806 after a journey of more than eight thousand miles and subsequently reported their findings to Jefferson. Numerous American communities celebrated the explorers along their journey home, but the immediate consequences of their discoveries went unrecognized. Jefferson had to fight Congressional critics who questioned the expedition’s expense, and extended accounts of the journey were not published until almost a decade after it had been completed.

Over the longer term, however, Lewis and Clark helped inspire growing popular sentiment in favor of western expansion and settlement, later dubbed “Manifest Destiny.” Although American Indians had generally, if not always, been helpful to the expedition’s success, the consequences for them as a people would ultimately be devastating, as western settlers and eventually the U.S. government encroached violently on their ancestral lands. Moreover, over the next few decades, the prospect of expansion into the Louisiana Territory and the addition of several new states to the Union brought the problem of the expansion of slavery to the forefront of political life and helped provoke the Civil War.

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Review Questions

1. A slave revolt in which country ruined Napoleon’s dreams of French dominance in North America?

1. Haiti
2. Cuba
3. The United States
4. Canada

2. The Louisiana Purchase opened which vital river to commerce and exploration?

1. The Potomac River
2. The Mississippi River
3. The Colorado River
4. The St. Lawrence River

3. The Louisiana Purchase is consistent with Jeffersonian-Republican philosophy because it

1. allowed for the expansion of an agrarian America
2. provided a specific constitutional method for acquiring new territory
3. promised the expansion of slavery into the western territories
4. drew the United States closer to a declaration of war against Great Britain

4. President Thomas Jefferson directed the Corps of Discovery under Meriwether Lewis to do all the following except

1. look for an all-water route to the Pacific Ocean
2. gather scientific information
3. inform Native Americans along the way that the land now belonged to the United States
4. concentrate exploration efforts to the east of the Continental Divide

5. The actions of Meriwether Lewis and William Clark under the banner of the Corps of Discovery are most consistent with

1. a belief in Manifest Destiny
2. the Second Great Awakening
3. the Seneca Falls Convention
4. utopian communitarianism

6. The purchase of the Louisiana Territory started as an attempt to

1. push the Spanish out of western Florida
2. secure access to the port of New Orleans
3. provide a southern terminus for the Erie Canal
4. gain control over the fertile farmland of west Texas

Free Response Questions

1. Explain Thomas Jefferson’s reasons for dispatching the Lewis and Clark expedition to explore the Louisiana Territory.
2. Explain the constitutional questions raised by the proposed purchase of the Louisiana Territory.
3. Evaluate the success of the Lewis and Clark expedition.

AP Practice Questions

“The object of your mission is to explore the Missouri river, & such principal stream of it, as, by [its] course & communication with the water of the Pacific ocean may offer the most direct & practicable water communication across this continent, for the purposes of commerce.

Beginning at the mouth of the Missouri, you will take observations of latitude and longitude at all remarkable points on the river . . .

The interesting points of the portage between the heads of the Missouri & the water offering the best communication with the Pacific ocean should be fixed by observation, . . .

Your observations are to be taken with great pains & accuracy to be entered distinctly, & intelligibly for others as well as yourself, to comprehend all the elements necessary, . . .

The commerce which may be carried on with the people inhabiting the line you will pursue, renders a knolege of these people important. You will therefore endeavor to make yourself acquainted, as far as a diligent pursuit of your journey shall admit, with the names of the nations & their numbers; the extent & limits of their possessions; their relations with other tribes or nations; their language, traditions, monuments; . . .

Other objects worthy of notice will be . . . the soil & face of the country . . . the animals of the country . . . the mineral productions of every kind.”

Thomas Jefferson to Captain Meriwether Lewis dated June 20, 1803

Refer to the excerpt provided.

1. The instructions in the excerpt best illustrate that the author has been influenced by

1. the Enlightenment
2. Anti-Federalists
3. the First Great Awakening
4. the Second Great Awakening

2. The excerpt most directly reflects a growing belief that

1. nationalism would be replaced by sectionalism
2. isolationism would lead to conflict
3. multiculturalism would strengthen the American national character
4. commerce across the continent was an important goal

3. The excerpt is most sharply focused on which of the following goals?

1. Cultivation of crops
2. Facilitation of commerce
3. Conquest of territory
4. Elimination of foreign threats

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Primary Sources

Mouton, Gary E., ed. Journals of the Lewis and Clark expedition: https://lewisandclarkjournals.unl.edu/

Suggested Resources

Ambrose, Stephen E. Undaunted Courage: Meriwether Lewis, Thomas Jefferson, and the Opening of the American West. New York: Simon & Schuster, 1996.

Boles, John B. Jefferson: Architect of Liberty. New York: Basic Books, 2017.

Kukla, Jon. A Wilderness So Immense: The Louisiana Purchase and the Destiny of America. New York: Knopf, 2003.

Ronda, James P. Finding the West: Explorations With Lewis and Clark. Albuquerque, NM: University of New Mexico Press, 2001.

Tubbs, Stephanie Ambrose, and Clay Jenkinson. The Lewis and Clark Companion: An Encyclopedic Guide to the Voyage of Discovery. New York: Henry Holt, 2003.