[This has been rewritten from 2025  and includes more sources along with suggested reading.]

In 1803 the United States purchased the Louisiana Territory from France for the price of 3 cents per acre for 828,000 miles of land. Next to the purchase of Alaska from Russia later in the century, it is one of the best land deals in United States history.

Outside of general descriptions, the exact contents of the territory were unknown. President Jefferson commissioned a “Corps of Discovery” to be headed up by Captain Meriwether Lewis and Lieutenant William Clark. It was not only to map the new land purchase but to explore the Pacific Northwest as well to see if any possible Northwest Passage (a water route between the Atlantic and Pacific Oceans) existed. Meriwether Lewis, who had both military and frontier experience and was Jefferson’s private secretary was selected by President Jefferson. William Clark, who had both military and frontier experience, had notable skills in navigation and cartography, was selected as co-captain by Lewis as he had served under him.

On 14 May 1804 the Corps of Discovery left St. Louis with 45 men (soldiers, interpreters, and boatmen) to begin their journey into the newly purchased American interior. Traveling up the Missouri River in six canoes and two longboats, they would winter in Dakota. Then they headed into Montana encountering the Rocky Mountains and met the Shoshone on the other side of the Continental Divide. They purchased horses from them and continued into the Bitterroot Mountains, down the rapids of the Clearwater and Snake Rivers, reaching the Columbia River and eventually the Pacific Ocean arriving on 8 November 1805. They paused there for the winter and headed back to St. Louis in the spring arriving on 23 September 1806.

They had traveled an astonishing 8,000 miles compiling detailed information that gave the first detailed look on the new territory and on the Pacific Northwest as well. They catalogued everything they saw on the journey–plants, animals, birds, minerals, people encountered, the mountains and rivers they saw–making their report one of the most consequential in the history of the United States. The report confirmed the newly purchased land had navigable rivers, land for people to settle on with plenty of game. They documented 122 animal species and 178 plants that were unknown till then. Their sketches, descriptions, and samples they brought back would excite the scientific world. And their detailed maps with coordinates would help further explorers and settlers. Other explorers like John C. Fremont found that their calculations as to the locations of rivers and other places were reliable; there were no major revisions and only minor ones that were done.

During their journey they encountered many diseases and ailments but only one person, Sergeant Charles Floyd, died during the journey from what now is believed to be acute appendicitis. A medical kit supplied by President Jefferson helped them on their journey, but sometimes contaminated water consumed on the journey resulted in occasional dysentery outbreaks. In addition to the medical kit, they did use natural remedies for fevers and other issues. Despite often poor sanitation and dealing with mosquitoes, they made the journey and returned home.

Sources

Buckley, Jay H. “Lewis and Clark Expedition.” Encyclopedia Britannica. Accessed May 19, 2026. https://www.britannica.com/event/Lewis-and-Clark-Expedition.

Peck, David J. “Wilderness Medicine.” Discover Lewis & Clark. Last modified March 27, 2023. Accessed May 19, 2026. https://lewis-clark.org/sciences/medicine/wilderness-medicine/.

“Corps of Discovery – Gateway Arch National Park (U.S. National Park Service).” Accessed May 19, 2026. https://www.nps.gov/jeff/learn/historyculture/corps-of-discovery.htm.

“Lewis and Clark: Expedition, Purpose & Facts | HISTORY.” HISTORY. Last modified April 20, 2026. Accessed May 19, 2026. https://www.history.com/articles/lewis-and-clark.

“Lewis & Clark Expedition.” National Archives. Last modified June 2, 2021. Accessed May 19, 2026. https://www.archives.gov/education/lessons/lewis-clark.

“Home | Journals of the Lewis and Clark Expedition.” Journals of the Lewis and Clark Expedition. Accessed May 19, 2026. https://lewisandclarkjournals.unl.edu/.

Documentaries & Videos

Biography. “Lewis & Clark: Explorers of the New Frontier | Full Documentary | Biography.” Video. YouTube, October 29, 2021. https://www.youtube.com/watch?v=DhPBfnDkO2w.

The History Guy: History Deserves to Be Remembered. “Seaman: Meriwether Lewis’ Dog.” Video. YouTube, November 6, 2024. https://www.youtube.com/watch?v=4QxOEXIikls.

River Museum. “Lewis & Clark: Great Journey West.” Video. YouTube, October 5, 2017. https://www.youtube.com/watch?v=vrRvPmKQ5uU.

Suggested Reading

[Disclosure: As an Amazon Associate, I earn from qualifying purchases. This post may contain affiliate links, which means I may receive a small commission at no extra cost to you.]

Ambrose, Stephen E. Undaunted Courage: Meriwether Lewis Thomas Jefferson and the Opening of the American West. Simon & Schuster, 2002.

Duncan, Dayton, and Ken Burns. Lewis & Clark: An Illustrated History. Knopf Publishing Group, 1997.

Fenster, Julie M. Jefferson’s America: The President, the Purchase, and the Explorers Who Transformed a Nation. Crown, 2017.

Gilman, Carolyn. Lewis and Clark: Across the Divide. Smithsonian, 2003.

Lewis, Meriwether, and William Clark. The Journals of Lewis and Clark. Penguin, 2002.

Tubbs, Stephenie Ambrose. Why Sacagawea Deserves the Day off & Other Lessons From the Lewis and Clark Trail. U of Nebraska Press, 2008.

On September 23, 1806, amid great public excitement, the expedition of William Clark and Meriwether Lewis returned to St. Louis, Missouri. They were the first to record an overland journey from the Mississippi River to the Pacific coast and back. Setting out in May 1804, they returned with extensive knowledge of the Louisiana Purchase territory.

In 1803, under President Jefferson, the United States purchased the Louisiana Territory for 3 cents per acre, totaling 828,000 square miles—one of the best land deals in history. Jefferson commissioned Lewis and Clark to explore this territory. The expedition, with about 48 men, traveled up the Missouri River in six canoes and two longboats, wintered in Dakota, and crossed into Montana, where they first saw the Rocky Mountains. They met the Shoshone Indians, who sold them horses, and journeyed through the Bitterroot Mountains, down the Clearwater and Snake rivers, reaching the Columbia River and the Pacific Ocean on November 8, 1805—the first European explorers to do so overland from the east. They wintered there before returning to St. Louis in spring.

Their journals recorded longitude, latitude, soil, climate, animals, plants, and native peoples, identifying new species like the grizzly bear and naming geographic locations after themselves, loved ones, friends, and their dog. Despite diseases and injuries, only one person died. Their expedition, one of the most consequential in U.S. history, helped establish U.S. territorial claims in Oregon.

Sources

Buckley and Jay H, “Lewis and Clark Expedition | Summary, History, Members, Facts, & Map,” Encyclopedia Britannica, last modified July 28, 2025, accessed September 9, 2025, https://www.britannica.com/event/Lewis-and-Clark-Expedition.

“Lewis and Clark Return to St. Louis | September 23, 1806 | HISTORY,” HISTORY, last modified May 28, 2025, accessed September 9, 2025, https://www.history.com/this-day-in-history/september-23/lewis-and-clark-return.

“Louisiana Purchase | Definition, Date, Cost, History, Map, States, Significance, & Facts,” Encyclopedia Britannica, last modified July 29, 2025, accessed September 9, 2025, https://www.britannica.com/event/Louisiana-Purchase.

Under President Jefferson, the United States purchased the Louisiana Territory in 1803 for a price of 3 cents per acre for some 828,000 square miles of land. It is considered one of the best land deals ever. Jefferson commissioned the expedition of Lewis and Clarke to explore this territory  from the Mississippi River to the Pacific Ocean. On 14 May 1804 this “Corps of Discovery” as it was called, left St. Louis with 45 men (only 33 would make the full journey) for the newly purchased American interior.

Traveling up the Missouri River in six canoes and two longboats they would winter in Dakota before crossing into Montana where they saw the Rocky Mountains for the first time. They would meet the Shoshone Indians on the other side of the Continental Divide, who would sell them horses. The journeyed through the Bitterroot Mountains, down the rapids of the Clearwater and Snake rivers, until they reached the Columbia River and to the sea. They arrived at the Pacific Ocean on 8 November 1805 and were the first European explorers to do this overland from the east. The paused for the winter and then made their journey back to St. Louis in the spring.

The journals that were kept noted longitude and latitude with detailed notes on soil, climate, animals, plants, and native peoples. They identified new plants and animals (the grizzly bear for one). They also named geographic locations after themselves, loved ones, friends and even their dog. They experienced a variety of diseases and injuries during their journey but only one person perished. Their expedition is considered one of the most consequential and remarkable in U.S. history. Their travels in Oregon would lead the U.S. to able claim territorial rights later.

Shop for books on Lewis & Clark expedition on Amazon

Sources

Buckley and Jay H, “Lewis and Clark Expedition | Summary, History, Members, Facts, & Map,” Encyclopedia Britannica, last modified April 21, 2025, https://www.britannica.com/event/Lewis-and-Clark-Expedition.

———. “Louisiana Purchase | Definition, Date, Cost, History, Map, States, Significance, & Facts.” Encyclopedia Britannica. Last modified April 25, 2025. https://www.britannica.com/event/Louisiana-Purchase.

HISTORY.com Editors, “Lewis and Clark: Expedition, Purpose & Facts | HISTORY,” HISTORY, last modified May 10, 2025, https://www.history.com/articles/lewis-and-clark.

Under President Jefferson, the United States purchased the Louisiana Territory in 1803 for a price of 3 cents per acre for some 828,000 square miles of land. It is considered one of the best land deals ever. Jefferson commissioned the expedition of Lewis and Clarke to explore this territory  from the Mississippi River to the Pacific Ocean. On 14 May 1804 this “Corps of Discovery” as it was called, left St. Louis with 45 men (only 33 would make the full journey) for the newly purchased American interior.

Traveling up the Missouri River in six canoes and two longboats they would winter in Dakota before crossing into Montana where they saw the Rocky Mountains for the first time. They would meet the Shoshone Indians on the other side of the Continental Divide, who would sell them horses. The journeyed through the Bitterroot Mountains, down the rapids of the Clearwater and Snake rivers, until they reached the Columbia River and to the sea. They arrived at the Pacific Ocean on 8 November 1805 and were the first European explorers to do this overland from the east. The paused for the winter and then made their journey back to St. Louis in the spring.

The journals that were kept noted longitude and latitude with detailed notes on soil, climate, animals, plants, and native peoples. They identified new plants and animals (the grizzly bear for one). They also named geographic locations after themselves, loved ones, friends and even their dog. They experienced a variety of diseases and injuries during their journey but only one person perished. Their expedition is considered one of the most consequential and remarkable in U.S. history. Their travels in Oregon would lead the U.S. to able claim territorial rights later.

Shop for books on Lewis & Clark expedition on Amazon

Sources:

Buckley, Jay H. “Lewis and Clark Expedition | Summary, History, Members, Facts, and Map.” Encyclopedia Britannica, 17 Apr. 2024, www.britannica.com/event/Lewis-and-Clark-Expedition.

—. “Lewis and Clark: Expedition, Purpose and Facts | HISTORY.” HISTORY, 28 Mar. 2023, www.history.com/topics/19th-century/lewis-and-clark.

—. “Louisiana Purchase | Definition, Date, Cost, History, Map, States, Significance, and Facts.” Encyclopedia Britannica, 25 Apr. 2024, www.britannica.com/event/Louisiana-Purchase.

This was first published in 2020. It has been updated in 2024 with new sources.

Under President Jefferson, the United States purchased the Louisiana Territory in 1803 for a price of 3 cents per acre for some 828,000 square miles of land. It is considered one of the best land deals ever. Jefferson commissioned the expedition of Lewis and Clarke to explore this territory  from the Mississippi River to the Pacific Ocean. On 14 May 1804 this “Corps of Discovery” as it was called, left St. Louis with 45 men (only 33 would make the full journey) for the newly purchased American interior.

Traveling up the Missouri River in six canoes and two longboats they would winter in Dakota before crossing into Montana where they saw the Rocky Mountains for the first time. They would meet the Shoshone Indians on the other side of the Continental Divide, who would sell them horses. The journeyed through the Bitterroot Mountains, down the rapids of the Clearwater and Snake rivers, until they reached the Columbia River and to the sea. They arrived at the Pacific Ocean on 8 November 1805 and were the first European explorers to do this overland from the east. The paused for the winter and then made their journey back to St. Louis in the spring.

The journals that were kept noted longitude and latitude with detailed notes on soil, climate, animals, plants, and native peoples. They identified new plants and animals (the grizzly bear for one). They also named geographic locations after themselves, loved ones, friends and even their dog. They experienced a variety of diseases and injuries during their journey but only one person perished. Their expedition is considered one of the most consequential and remarkable in U.S. history. Their travels in Oregon would lead the U.S. to able claim territorial rights later.

Sources:

• Lewis and Clark Expedition (Britannica.com)
• Lewis and Clark Return to St. Louis (History.com)
• Louisiana Purchase (Britannica.com)

Under President Jefferson, the United States purchased the Louisiana Territory in 1803 for a price of 3 cents per acre for some 828,000 square miles of land. It is considered one of the best land deals ever. Jefferson commissioned the expedition of Lewis and Clarke to explore this territory  from the Mississippi River to the Pacific Ocean. On 14 May 1804 this “Corps of Discovery” as it was called, left St. Louis with 45 men (only 33 would make the full journey) for the newly purchased American interior.

Traveling up the Missouri River in six canoes and two longboats they would winter in Dakota before crossing into Montana where they saw the Rocky Mountains for the first time. They would meet the Shoshone Indians on the other side of the Continental Divide, who would sell them horses. The journeyed through the Bitterroot Mountains, down the rapids of the Clearwater and Snake rivers, until they reached the Columbia River and to the sea. They arrived at the Pacific Ocean on 8 November 1805 and were the first European explorers to do this overland from the east. The paused for the winter and then made their journey back to St. Louis in the spring.

The journals that were kept noted longitude and latitude with detailed notes on soil, climate, animals, plants, and native peoples. They identified new plants and animals (the grizzly bear for one). They also named geographic locations after themselves, loved ones, friends and even their dog. They experienced a variety of diseases and injuries during their journey but only one person perished. Their expedition is considered one of the most consequential and remarkable in U.S. history. Their travels in Oregon would lead the U.S. to able claim territorial rights later.

Sources:

• Lewis and Clark Expedition (Britannica.com)
• Lewis and Clark Return to St. Louis (History.com)
• Louisiana Purchase (Britannica.com)