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Lewis and Clark Expedition

Encyclopedia Article from Encarta

Introduction Relations with Native Americans and Spanish
Background Relations Among the Explorers
Preparations Aftermath and Achievements
The Expedition Scientific Findings
The Voyage Westward The Fate of the Explorers
The Return Voyage Bicentennial Celebrations


Lewis and ClarkLewis and Clark Expedition, first United States overland exploration of the American West and Pacific Northwest, beginning in May 1804 and ending in September 1806. The expedition was commissioned by President Thomas Jefferson and led by army officers Meriwether Lewis and William Clark. The exploration covered a total of about 13,000 km (about 8,000 mi), from a camp outside St. Louis to the Pacific Ocean and back. Like other scholars in his time, Jefferson believed in the existence of a Northwest Passage, or some kind of water connection between the Atlantic and Pacific oceans. The principal goal of the expedition was to locate such a route and survey its potential as a waterway for American westward expansion. Although Lewis and Clark did not find this route, the expedition succeeded in making peaceful contact with Native Americans and uncovering a wealth of knowledge about the peoples, geography, plants, and animals of the western United States.


Although Jefferson had long been interested in the American West, it was not until 1802 that he began to plan an expedition to the Pacific. After reading Voyages from Montréal (1801) by Canadian explorer and fur trader Sir Alexander Mackenzie in the summer of 1802, the president began to make preparations for an American expedition aimed at countering Mackenzie’s plans to make the West and Pacific Northwest part of the British Empire. Influenced by the renowned 18th-century journeys of Captain James Cook and Captain George Vancouver, Jefferson envisioned an official expedition that combined diplomatic, scientific, and commercial goals. He believed that the nation that dominated a water passage through the continent could control the destiny of all North America. He was also convinced that the West would be a paradise for American farmers.


The president turned to his young private secretary, Captain Meriwether Lewis, for leadership in this enterprise. An army officer and experienced naturalist, Lewis had the background, energy, and dedication to fulfill the challenging assignment. In June 1803 Jefferson completed his demanding exploration instructions after receiving advice from leading American scientists, including physicians Benjamin Rush and Benjamin Smith Barton, and the noted surveyor Andrew Ellicott. In a detailed letter now recognized as a classic exploration document, Jefferson itemized more than a dozen areas of inquiry for the expedition, ranging broadly from astronomy and botany to linguistics and zoology.

The president sought information about plants, animals, rivers, mountains, and native cultures, which Lewis and Clark recorded in journals during the expedition.

The demands of the expedition were enormous, and Lewis soon turned to William Clark, a friend from his army days in Ohio, to act as co-commander. Despite the fact that Clark was officially a lieutenant, and therefore of lower rank than Lewis, a captain, Jefferson and Lewis considered Clark an equal leader of the party.

In 1803, after Jefferson had written his instructions for the team, the United States acquired a vast portion of the central North American continent from France in the Louisiana Purchase. The land purchase increased the importance of the expedition. Since the team would now be exploring United States lands, Lewis and Clark had the added duty of announcing American sovereignty in the new territory.

The Expedition

The Corps of Discovery, as the expedition party was properly known, demanded more people than Jefferson first imagined. Before reaching their base camp at Wood River outside St. Louis, Lewis and Clark recruited a sizable number of civilian hunters, army soldiers, and French boatmen. While not all made the entire journey to the Pacific, some 48 men were part of the team when it left St. Louis heading up the Missouri River. The expedition roster included Clark’s slave, York, who some Native Americans called "Big Medicine," along with many other adventurers who came to play a major role in American expansion, such as the hunters John Colter and George Drouillard. Other members of the expedition who also kept journals were Sergeants Charles Floyd, Patrick Gass, and John Ordway, and Private Joseph Whitehouse. The Corps and its supplies went up the river on a large keelboat (a riverboat used for freight) and several smaller boats, requiring the experience of French boatmen.

The Voyage Westward

The Corps of Discovery’s route across the continent was dictated by Jefferson’s notions of American geography. The president believed that the most practical passage across the continent followed the Missouri River to its headwaters in the Rocky Mountains. Once over the mountains by a presumably short and easy portage, Jefferson was sure that his explorers would find another river leading directly to the ocean. However, the president’s assumptions about geography did not match Western realities.

As commanding officers for the expedition, Lewis and Clark informally divided leadership responsibilities: Lewis became the party’s naturalist, and Clark served as the mapmaker and negotiator. The expedition set out on May 21, 1804. In its first season of travel (May to October 1804), the expedition made its way up the Missouri, built Fort Mandan in present-day North Dakota, and spent the winter among the Mandan and Hidatsa peoples. Although some of the travel was physically demanding, this stretch of the river already was well known to St. Louis merchants and traders. On August 20, 1804, near present-day Sioux City, Iowa, the expedition suffered its only fatality when Sergeant Charles Floyd died of a ruptured appendix.

The second travel season (April to December 1805) proved far more challenging as the expedition moved into country unknown to the nonnatives. The Corps of Discovery now counted 33 members in the permanent party, including a Native American woman, Sacagawea, her husband, French Canadian interpreter Toussaint Charbonneau, and their infant son Jean Baptiste, all of whom joined the group at Fort Mandan. Sacagawea, a Shoshone who had been captured by the Hidatsa tribe and then sold to Charbonneau, helped the party as an interpreter and peacemaker. She proved instrumental in negotiating for horses and supplies along the way.

The expedition struggled around the Great Falls of the Missouri, searched for a pass over the Continental Divide, and was stunned not to find a water passage direct from present-day Idaho to the ocean. Instead, the party labored in deep snow over the Lolo Trail, crossing the border of present-day Montana into Idaho, where they encountered the Native American tribe known as the Nez Perce. The Nez Perce taught them how to eat camas roots and assured them that the rivers ahead were navigable. The explorers then traveled on the Snake River into present-day Washington before finally reaching the Columbia River. By the time Lewis and Clark reached the Pacific Ocean in November 1805 and built Fort Clatsop, their winter residence near present-day Astoria, Oregon, they had a much clearer sense of the continent’s geographic complexity.

The Return Voyage

The return journey from Fort Clatsop to St. Louis (March to September 1806) held its own unique dangers and accomplishments. With several important exploration tasks still planned, Lewis and Clark divided the Corps of Discovery into two parties. Clark led one group on a reconnaissance of the Yellowstone River. Meanwhile, Lewis took a small detachment into present-day north central Montana, thinking that the course of the Marias River might provide an American claim to fur-rich country in what is now the Canadian province of Alberta. In August the groups reunited on the Missouri River, near the mouth of the Yellowstone. They arrived in St. Louis on September 23, 1806.

Relations with the Native Americans and Spanish

The Lewis and Clark Expedition made a journey through the homelands of native people. What American explorers called "wilderness" and "unknown" was more properly Native American homes, gardens, and hunting territories. Without the active support of native people, the expedition could not have accomplished its goals, much less survived in a sometimes-difficult country. Native people provided Lewis and Clark with vital geographic information, food, shelter, and transportation. In many ways Sacagawea symbolized the cooperation between native people and the Corps of Discovery. While she was not a guide in the fullest sense of the word, her presence assured many Native Americans that the Corps of Discovery was not a hostile war party. At a key juncture Sacagawea was reunited with her brother Cameahwait, a Shoshone chief who provided vital assistance to the expedition.

In two-and-a-half years of travel and exploration, there was only one fatal encounter between the Corps of Discovery and Native Americans. The incident occurred during Lewis’s exploration of the Marias River. In late July 1806 Lewis’s party came upon a group of Piegan Blackfoot warriors. When the Piegans attempted to take guns and horses, Lewis’s men retaliated, killing two natives.

While native people saw the expedition more as an opportunity for trade than as a threat to tribal sovereignty, Spanish officials in Mexico City had a different reaction to Jefferson’s enterprise. The Spanish had long been deeply suspicious of American ambitions in the West and since the end of the American Revolution (1775-1783) were certain that the new American republic intended to reach across the continent to the Pacific. Alerted to the Corps of Discovery, possibly by secret agent General James Wilkinson, the Spanish made several unsuccessful attempts to stop the expedition and capture Lewis and Clark.

Relations Among the Explorers

The explorers themselves were undoubtedly transformed by their journey. What began as a diverse and unruly set of characters became in the course of the expedition a tight-knit community. At Fort Mandan, Lewis described the expedition members as enjoying "a most perfect harmony."

Aftermath and Achievements

Lewis and Clark received a hero’s welcome when they returned from the expedition, despite some disappointment that they had not found an easy water route to the Pacific. After Lewis’s death in 1809, Clark and American diplomat and financier Nicholas Biddle took over the task of compiling the report. They finally published an abridged, two-volume collection of the journals in 1814. This version left out most of the material the party had compiled about plant and animal life. The most recent scholarly edition of the journals was edited in 11 volumes by historian Gary E. Moulton under the title, The Journals of the Lewis and Clark Expedition, and published from 1983 to 1997 by the University of Nebraska Press.

Thomas Jefferson had repeatedly insisted that the Corps of Discovery had one central mission—to find what he called "the most direct and practicable water communication across this continent for the purposes of commerce." However, Lewis and Clark did not find a Northwest Passage, nor did they pioneer the route that became the Oregon Trail. Although Lewis and Clark strengthened U.S. claims in the West, American claims in subsequent diplomatic disputes with Britain were based not so much on Lewis and Clark as on the Columbia River explorations of American explorer Captain Robert Gray in 1792 and the building of Fort Astoria in 1811. But Jefferson was by no means disappointed with his Corps of Discovery. The journals, maps, plant and animal specimens, and notes on Native American societies amounted to a Western encyclopedia.

The expedition also established peaceful contact with many Native American peoples. Finally, the expedition set a pattern for government-sponsored scientific exploration in the United States.

Scientific Findings

The Lewis and Clark Expedition discovered 122 animal species and subspecies and 178 new plant species, and 223 plant specimens from the expedition survive. Among the animal species and subspecies previously unknown to science were the grizzly bear, the California condor, the coyote, the black-footed ferret, the black-billed magpie, the black-tailed prairie dog, the pronghorn, and the gray wolf. The two explorers left their names imprinted on two bird species, Lewis’s woodpecker and Clark’s nutcracker, and the scientific name for the westslope cutthroat trout (Oncorhynchus clarki lewisi). Among the plant species they described for science for the first time were the western red cedar, eastern cottonwood, red flowering currant, the mountain hemlock, the whitebark pine, Sitka spruce, Oregon grape, and the Pacific yew.

A trained naturalist, Lewis was especially noted for his meticulous observations and exacting measurements of new species. Perhaps more important for the future settlement of the West, Lewis and Clark returned with stories of the rich abundance of wildlife.

The Fate of the Explorers

Following the expedition, President Jefferson appointed Lewis the governor of the new Louisiana Territory. Lewis reportedly struggled with the demands of the position, fell into a depression, and three years after the expedition’s end, most historians agree, committed suicide. In 1807 Clark was appointed as the U.S. government’s representative to the Native American tribes living west of the Mississippi River, a role he retained until his death in 1838. Clark initially refused York’s requests that he be given his freedom in exchange for his service to the expedition but eventually relented in 1816. York went into the freight business and reportedly died in 1832. Sacagawea died in 1812 at the age of 25 at Fort Manuel in present-day South Dakota. Her two children, Jean Baptiste and a daughter Lisette who was born after the expedition, were adopted by Clark. Her husband Charbonneau continued living among the Mandan and Hidatsa. His death date is unknown but his estate was settled in 1843 by his son Jean Baptiste, the youngest member of the expedition.

Bicentennial Celebrations

More than 200 years after the Lewis and Clark expedition was first commissioned, the journey still captures the imagination of the American people. It was not always so. The first history of the expedition, published in 1814, saw only 1,417 copies printed. By the mid-1800s, the expedition was largely forgotten. Since then, however, the fame of the expedition has grown considerably. Bicentennial celebrations in the United States began in January 2003, the anniversary of Jefferson’s request to Congress for funding. Over the course of the next four years, more than 30 million people were expected to travel to some part of the Lewis and Clark trail as part of the bicentennial commemoration. Parts of the trail, such as the White Cliffs of the Upper Missouri River, the Lemhi Pass in the Rocky Mountains, along the Lolo Trail in Idaho, and portions of the Columbia River estuary are considered nearly unchanged since the time of the expedition.