Lewis and Clark Expedition Summary

  • Last updated on November 10, 2022

The first major transcontinental exploratory expedition in North America, the Lewis and Clark expedition, opened the Louisiana Territory to settlement and trade and reinforced U.S. claims to the Oregon region on the Pacific coast.

Summary of Event

Meriwether Lewis, William Clark, and their companions were the first Europeans to cross the western half of what became the continental United States. They traveled through the future states of Missouri, Missouri;exploration of Kansas Kansas;exploration of , Nebraska, Nebraska;exploration of South Dakota South Dakota;exploration of , North Dakota North Dakota;exploration of , Montana Montana;exploration of , Idaho, Idaho;exploration of Washington Washington State;exploration of , and Oregon Oregon;exploration of . Their two-year-long expedition was the concluding act in the long and fruitless search for a water route through the continent—a northwest passage Northwest Passage;and Lewis and Clark expedition[Lewis and Clark expedition] —that had begun soon after Christopher Columbus discovered the New World at the end of the fifteenth century. Lewis and Clark expedition Exploration;North America Lewis, Meriwether Clark, William Sacagawea [kw]Lewis and Clark Expedition (May 14, 1804-Sept. 23, 1806) [kw]Clark Expedition, Lewis and (May 14, 1804-Sept. 23, 1806) [kw]Expedition, Lewis and Clark (May 14, 1804-Sept. 23, 1806) Lewis and Clark expedition Exploration;North America Lewis, Meriwether Clark, William Sacagawea [g]United States;May 14, 1804-Sept. 23, 1806: Lewis and Clark Expedition[0240] [c]Exploration and discovery;May 14, 1804-Sept. 23, 1806: Lewis and Clark Expedition[0240] [c]Geography;May 14, 1804-Sept. 23, 1806: Lewis and Clark Expedition[0240] Drouillard, George Charbonneau, Toussaint York Jefferson, Thomas [p]Jefferson, Thomas;and Lewis and Clark expedition[Lewis and Clark expedition]

Meriwether Lewis (right) and William Clark (left).

The instigator of the expedition was President Thomas Jefferson, Jefferson, Thomas [p]Jefferson, Thomas;and Lewis and Clark expedition[Lewis and Clark expedition] who first thought of such an undertaking around the time that the United States achieved its independence in 1783. During the ensuing decade he twice tried unsuccessfully to launch a transcontinental exploring party. Not until he assumed the presidency in 1801, however, was he in a position to have his plan implemented. On January 18, 1803, the president asked Congress to authorize an appropriation of twenty-five hundred dollars to send a military expedition to explore the Missouri River Missouri River up to its source in the Rocky Mountains Rocky Mountains;exploration of , and then down the nearest westward-flowing streams to the Pacific Ocean. Jefferson gave two reasons for the proposed expedition: to prepare the way for the extension of the American fur trade Fur trade;and Lewis and Clark expedition[Lewis and Clark expedition] to the Native American peoples throughout the area to be explored and to advance geographical knowledge of the continent.

When Jefferson sent his message to Congress, none of the territory that he proposed to explore lay within the United States. At that time, the immense region between the Mississippi River and the Rocky Mountains—all of which was collectively known as Louisiana—belonged to France. Parts of the Pacific Northwest were claimed by Great Britain, Spain, Russia, and the United States. While Jefferson Jefferson, Thomas [p]Jefferson, Thomas;and Lewis and Clark expedition[Lewis and Clark expedition] was developing his plans for a transcontinental exploring expedition, however, he also was overseeing negotiations with the French government of Napoleon Bonaparte. These talks resulted in the purchase of Louisiana from France through a treaty signed in May, 1803. Thus, by the time the expedition was finally launched, it not only explored U.S. territory but also strengthened the U.S. claim to the region beyond the Rocky Mountains.

Lewis and Clark Expedition, 1804-1806





To command the expedition, Jefferson chose his private secretary, Captain Meriwether Lewis. With Jefferson’s approval, Lewis then invited his longtime friend William Clark to be his coleader. After making initial preparations in the East, Lewis traveled to Wood River, Illinois, opposite the mouth of the Missouri River. Clark and several recruits joined him on the way down the Ohio River Ohio River . Lewis and Clark then spent the winter of 1803-1804 at Camp Wood River recruiting and training their men, gathering additional equipment and supplies—which included fourteen bales of trade goods—and collecting information about the Missouri River Missouri River from traders and boatmen.

The expedition party eventually included twenty-seven young, unmarried soldiers; a mixed-blood hunter and interpreter named George Drouillard; Drouillard, George Clark’s black slave, York York ; and Lewis’s big Newfoundland dog, Scammon. An additional body comprising an army corporal, five privates, and several French boatmen was to accompany the main expedition party through its first season and then return down the Missouri River with the expedition’s records, sketches, and scientific specimens.

Officially known as the Corps of Discovery, the expedition began its historic journey at the confluence of the Missouri and Mississippi Rivers. On May 14, 1804, it started traveling up the Missouri River Missouri River in a fifty-five-foot keelboat and two dugout canoes. The expedition reached the villages of the Mandan Mandan and Minnataree Minnataree people, near the mouth of the Knife River in the future state of North Dakota, at the end of October after traveling about 1,600 miles (2,575 kilometers). There the explorers built a log stronghold called Fort Mandan Fort Mandan and went into winter quarters.

During the long, frigid winter that followed, Lewis and Clark made copious notes in their journals, drew maps of their route, and met with numerous Native American visitors. From the Minnatarees, especially, they obtained invaluable information about the course of the Missouri River and the country through which it ran. The contributions of these and other Native Americans to the success of the exploration cannot be overstated. Finally, on April 7, 1805, the expedition resumed its journey. The party now numbered only thirty-three persons. In addition to the permanent detachment, the party included the French interpreter Toussaint Charbonneau; Charbonneau, Toussaint his young Shoshone wife, Sacagawea; and their two-month-old son, Jean Baptiste, who was nicknamed Pompey. After passing through country never before visited by Europeans, the expedition reached the navigable limits of the Missouri River Missouri River on August 17.

With Sacagawea’s help, Lewis and Clark purchased horses from her brother Cameahwai Cameahwai of the Shoshone people and began their journey through the Rocky Mountains Rocky Mountains;exploration of . Three years earlier, Sacagawea had been captured by a Minnataree Minnataree raiding party, which carried her east to the prairie, where Charbonneau had purchased her for his wife. The chance meeting of Sacagawea and her brother, who had become the chief of their clan, was a convenient opportunity for the expedition. Along with the horses, Lewis and Clark were given travel instructions and lent a guide, called Toby, to assist them through the mountains. After crossing the mountains, the explorers descended the Clearwater, Snake, Snake River and Columbia Rivers Columbia River to the Pacific Ocean, where they arrived in mid-November.

After a dreary winter at Fort Clatsop Fort Clatsop , south of the Columbia River, the explorers started for home on March 23, 1806. Other than fighting to keep warm and searching for food, the highlight of their Pacific coast stay was a visit to the remains of a beached whale, from which they obtained 300 pounds (136 kilograms) of blubber and oil. They were anxious to return east, as they saw the sun only on six days during their stay at Fort Clatsop.

On their return journey, the party divided temporarily. Lewis and a small party explored the Marias River, while Clark and the rest of the expedition descended the Yellowstone River. The entire expedition reunited below the mouth of the Yellowstone, then hurried down the Missouri and arrived in St. Louis on September 23, 1806.


The Lewis and Clark expedition accomplished its mission with remarkable success. During more than twenty-eight months, it traveled more than 8,000 miles (12,875 kilometers). During the entire journey, only one man, Sergeant Charles Floyd Floyd, Charles , lost his life—apparently from a ruptured appendix. Although the explorers met thousands of Native Americans, they had only one violent encounter with them. That incident occurred while Lewis was high up the Marias River and resulted in the death of two Piegan members of the Blackfoot Confederacy.

The total expense of the undertaking, including the special congressional appropriation of $2,500, was $38,722.25. Charbonneau Charbonneau, Toussaint collected $500.33 for his and Sacagawea’s services. For this comparatively small cost to the federal government, Lewis and Clark and their companions took the first giant step in opening the West to the American people.

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Ambrose, Stephen E. Undaunted Courage: Meriwether Lewis, Thomas Jefferson, and the Opening of the American West. New York: Simon & Schuster, 1996. Best-selling account by a prominent historian who retraced the expedition’s route to the Pacific and painstakingly re-created the activities and discoveries of the journey.
  • citation-type="booksimple"

    xlink:type="simple">Biddle, Nicholas, and Paul Allen, eds. History of the Expedition Under the Command of Captains Lewis and Clark. 2 vols. Philadelphia: J. B. Lippincott, 1961. Prepared between 1810 and 1814 by Nicholas Biddle, a young Philadelphia lawyer, this work is based on both Lewis’s and Clark’s journals.
  • citation-type="booksimple"

    xlink:type="simple">De Voto, Bernard, ed. The Journals of Lewis and Clark. Boston: Houghton Mifflin, 1953. A one-volume condensation of the Original Journals of Lewis and Clark Expedition. Includes maps.
  • citation-type="booksimple"

    xlink:type="simple">Jones, Landon Y. William Clark and the Shaping of the West. New York: Hill & Wang, 2004. Focuses on Clark’s private life and public career in the thirty years following his expedition with Lewis. Includes discussions of Clark’s duties in the Kentucky militia, his service as governor of the Missouri Territory, and his role as superintendent of Indian affairs at St. Louis.
  • citation-type="booksimple"

    xlink:type="simple">McGrath, Patrick. The Lewis and Clark Expedition. Morristown, N.J.: Silver Burdett, 1985. A simple but complete telling of the Lewis and Clark adventure for younger readers.
  • citation-type="booksimple"

    xlink:type="simple">Ronda, James P. Lewis and Clark Among the Indians. Lincoln: University of Nebraska Press, 1984. An important and engaging ethnohistorical study, this work chronicles the daily contact between the explorers and Indians and shows that the expedition initiated important economic and diplomatic relations with them.
  • citation-type="booksimple"

    xlink:type="simple">Slaughter, Thomas P. Exploring Lewis and Clark: Reflections on Men and Wilderness. New York: Random House, 2003. A revisionist view of the expedition in which Slaughter attempts to correct the myths and legends that he believes have surrounded it.
  • citation-type="booksimple"

    xlink:type="simple">Tourtelott, Jonathan B., ed. “Meriwether Lewis/William Clark.” In Into the Unknown: The Story of Exploration. Washington, D.C.: National Geographic Society, 1987. A thirty-four-page chapter devoted to the Lewis and Clark expedition.

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Categories: History