Into the Unknown: How Lewis and Clark’s Corps of Discovery Changed America Forever

On a showery Monday afternoon, May 14, 1804, a fleet of three vessels — a 55-foot keelboat and two flat-bottomed pirogues — pushed off from the muddy banks of Camp Dubois into the Missouri River. The men at the oars didn’t know exactly what lay ahead. Nobody did. That was precisely the point.

AT A GLANCE Departure date: May 14, 1804 (approximately 4 PM), Camp Dubois (Camp Wood), Illinois Commanded by: Captain Meriwether Lewis & Second Lieutenant William Clark (addressed as “Captain” by all) Crew: ~45 members: soldiers, civilian volunteers, French-Indian interpreter, York (enslaved by Clark), and Seaman, the Newfoundland dog Vessels: One 55-foot keelboat and two pirogues (flat-bottomed boats) Official name: Corps of Volunteers for Northwest Discovery — “Corps of Discovery” Mission: Explore the Louisiana Purchase, find a water route to the Pacific, document flora/fauna, and establish relations with Native nations Total distance: ~8,000 miles over 28 months Journey’s end: September 23, 1806 — return to St. Louis Species documented: 178 new plant species; 122 new animal species Only fatality: Sgt. Charles Floyd — appendicitis, August 20, 1804, near present-day Sioux City, Iowa

A Nation with New Land It Had Never Seen

In the summer of 1803, the United States made arguably the greatest real estate transaction in history. The Louisiana Purchase, finalized on May 2, 1803, added approximately 828,000 square miles of land west of the Mississippi River to the young republic — purchased from France for roughly $15 million, or about three cents per acre. The nation had doubled in size virtually overnight. There was only one problem: almost no Americans had ever been there. The vast interior was known only to the Native nations who had lived upon it for millennia, and to the occasional French and Spanish traders who had mapped only its edges.

President Thomas Jefferson had been dreaming of western exploration long before the Louisiana Purchase made it urgent. As early as 1792, Jefferson had instructed naturalist André Michaux to explore the Missouri River corridor toward the Pacific. That mission never launched. But with the stroke of a pen in 1803, Jefferson now had both the land and a compelling national need to understand what America had purchased.[1]

Jefferson’s instructions to his chosen expedition leader were sweeping. In a letter dated June 20, 1803, he directed the expedition to “explore the Missouri River and such principal streams of it, as by its course and communication with the waters of the Pacific Ocean” for the purposes of commerce. But Jefferson wanted far more than a trade route: he wanted a complete scientific inventory of the continent — its geology, flora, fauna, climate, indigenous peoples, languages, and cultures.[2]

Meriwether Lewis: The Reluctant Explorer

Meriwether Lewis was born on August 18, 1774, in Albemarle County, Virginia, a close neighbor to Jefferson’s Monticello. His father died when Lewis was just five years old, and he grew up in Georgia before returning to Virginia to complete his education. By 1795, he had joined the U.S. Army, where he proved himself a capable officer with a naturalist’s eye for the world around him. In 1801, newly elected President Jefferson invited Lewis to serve as his private secretary, less a clerical role than a position as Jefferson’s eyes and ears in the young federal government. Jefferson later described his choice of Lewis as expedition leader with characteristic precision:

“It was impossible to find a character who to a complete science in botany, natural history, mineralogy & astronomy, joined the firmness of constitution & character, prudence, habits adapted to the woods & a familiarity with the Indian manners and character, requisite for this undertaking.” — President Thomas Jefferson, explaining his selection of Meriwether Lewis to lead the Corps of Discovery

To prepare Lewis for the expedition, Jefferson arranged an intensive course of study in Philadelphia in the spring of 1803. Under the tutelage of leading American scientists, including physician Benjamin Rush, astronomer Andrew Ellicott, mathematician Robert Patterson, and naturalist Benjamin Smith Barton, Lewis spent several weeks absorbing the disciplines he would need in the field: medicine, celestial navigation, botany, natural history, and ethnography. It was an extraordinary effort to equip one man with the knowledge of an entire scientific institution — because he would be the only one available for thousands of miles.

Lewis was also a man of deep and sometimes volatile emotions. Historians have noted that he likely suffered from some form of depression, and his life after the expedition was marked by personal and professional difficulties. He died under mysterious circumstances in 1809, likely by suicide, at a Tennessee inn on the Natchez Trace while traveling to Washington. He was 35. The journals he had promised to publish had not yet been completed. It fell to William Clark — and ultimately to writer Nicholas Biddle — to bring the expedition’s account to print.

William Clark: The Steady Hand

William Clark was born on August 1, 1770, in Caroline County, Virginia, the ninth of ten children in a family that moved to Kentucky when Clark was fourteen. His older brother George Rogers Clark had been a celebrated Revolutionary War general, and military service was in William’s blood. He joined the Kentucky militia at nineteen, then transferred to the regular U.S. Army, where he served as a lieutenant of infantry — and where, in 1795, he first encountered a young ensign named Meriwether Lewis under his command.

Clark left the Army in 1796 to manage the family estate in Kentucky. Still, when Lewis’s letter arrived in the summer of 1803, inviting him to co-lead an expedition into the unknown west, he accepted within two weeks. Lewis wanted shared command, and although the War Department refused — allowing Clark only a lieutenant’s rank rather than a captain’s — Lewis concealed this from the rest of the Corps, and the two men led as equals throughout the entire journey.[3]

Where Lewis was the expedition’s scientist, naturalist, and diplomat, Clark was its waterman, cartographer, and logistician. He had a gift for reading rivers and drawing maps, and his charts of the Missouri and Columbia river systems — compiled from his own observations and from conversations with Native guides — would become the most accurate maps of the American West produced in the early 19th century. He also had a steadier temperament. While Lewis’s journal entries could be lyrical, melancholic, or deeply philosophical, Clark’s tended toward the practical and precise — a complementary combination that served the expedition well.

After the expedition, Clark had a long and influential public career. He served as superintendent of Indian affairs for the Louisiana Territory and later as governor of the Missouri Territory, a role in which he was a central figure in federal relations with Native nations for decades. He died in St. Louis in 1838 at age 68, the last surviving member of the original expedition’s leadership. He had never freed York, the enslaved man who had served the expedition loyally and contributed to its success, until long after their return, a moral failure that shadows his legacy.

May 14, 1804: “Set Out at 3 O’Clock P.M.”

The Corps of Discovery had spent the winter of 1803–04 at Camp Dubois — also called Camp Wood or Camp River Dubois — at the confluence of the Missouri and Mississippi rivers near present-day Hartford, Illinois. Clark recruited and drilled the men through the cold months while Lewis conferred with traders and officials in St. Louis, gathering maps and intelligence about the upper Missouri. The official transfer of Upper Louisiana from France to the United States on March 10, 1804, cleared the final diplomatic hurdle, and the Corps prepared for departure.[4]

The journal entry for May 14, 1804, recorded by expedition member Joseph Whitehouse, is spare and matter-of-fact: “Showery day. Capt. Clark Set out at 3 o’clock P.M. for the western expidition. the party Consisted of 3 Sergts and 38 working hands which maned the Batteaw and two Perogues. we Sailed up the Missouria 6 miles and encamped on the N. side of the River.”[5]

Lewis, who was still in St. Louis handling last-minute logistical business, would join the Corps at St. Charles, Missouri, about six days later. But May 14 was the official departure date — the day Clark noted in his own journal that “The mouth of the River Dubois is to be considered as the point of departure.” The party numbered roughly 45 men in total, including 27 unmarried soldiers chosen for their skills, a French-Indian interpreter, contracted French boatmen who would accompany them only to the Mandan villages, and York, the enslaved African American man who belonged to Clark and whose strength, skill, and remarkable effect on the Native peoples encountered by the Corps would prove invaluable throughout the journey.

The keelboat Lewis had designed and supervised the construction of — a 55-foot craft with a single mast and 22 oars — was the expedition’s workhorse. It carried the bulk of the supplies: scientific instruments, gifts for Native nations, medicine, tools, weapons, and enough provisions to sustain the party for months in a country where resupply was impossible. Lewis had also purchased, for $20, a large Newfoundland dog he named Seaman, who would travel the entire journey with the Corps and appear in the journals as companion, guard dog, and occasional dinner conversation.

Two Years, 8,000 Miles, a Continent Mapped

The journey that followed May 14, 1804, would unfold over twenty-eight months and cover approximately 8,000 miles. The Corps traveled up the Missouri River through the present-day states of Missouri, Kansas, Iowa, Nebraska, and South Dakota, fighting strong currents, heat, insects, and the treacherous, snag-filled river at an average pace of about 15 miles per day. On August 20, 1804, Sergeant Charles Floyd died of what is believed to have been a ruptured appendix — the only death of the entire expedition.

By October 1804, the Corps reached the Mandan and Hidatsa villages in present-day North Dakota, where they built Fort Mandan and spent the winter. There, they hired French-Canadian trapper Toussaint Charbonneau as interpreter, along with his teenage Shoshone wife, Sacagawea, who had been captured by an enemy tribe years earlier and sold into the trapper’s household. Sacagawea’s role in the expedition would prove indispensable: she served as interpreter, cultural guide, and living symbol of peaceful intent to the tribes they encountered. Her infant son, Jean Baptiste, born February 11, 1805, traveled the entire journey strapped to a cradleboard.

On April 7, 1805, the permanent Corps — now numbering 33 — set out again westward into territory no American citizen had seen. They followed the Missouri to its headwaters in the Rockies, crossed the Continental Divide at Lemhi Pass in present-day Montana with horses purchased from Sacagawea’s Shoshone people, then descended the Clearwater, Snake, and Columbia rivers in dugout canoes. On November 7, 1805, Clark wrote in his journal: “Ocean in view! O! the joy!” They had reached the Pacific.

After a winter at Fort Clatsop on the Oregon coast, the Corps began its return journey on March 23, 1806. Lewis and Clark divided their party for part of the return to explore additional routes, then reunited on the Missouri. On September 23, 1806, the Corps of Discovery paddled back into St. Louis — to the astonishment of the city’s residents, who had long since given them up for dead. They had been gone two years, four months, and ten days.

What They Brought Back: A Scientific Treasure

The intellectual yield of the Corps of Discovery was staggering. Lewis identified 178 plant species previously unknown to science, including bitterroot, prairie sagebrush, Douglas fir, and ponderosa pine. He documented 122 animal species, including the grizzly bear, prairie dog, pronghorn antelope, and mountain goat. Clark’s maps of the Missouri-Columbia river system remained the most accurate representations of the American West for decades, informing every subsequent wave of exploration and settlement.

The Corps also made peaceful diplomatic contact with more than 50 indigenous nations, presenting each with Jefferson’s “peace medal” and conducting formal councils to establish trade relations with the United States. Lewis and Clark’s journals recorded the languages, customs, governance structures, and material cultures of these nations with a level of detail that has proven invaluable to historians and tribal nations alike. The record was deeply imperfect — shaped by the biases of its authors and the politics of expansion — but it was also irreplaceable.

The journals were eventually published in 1814, edited by Philadelphia lawyer Nicholas Biddle. But the original handwritten documents — Clark’s maps, Lewis’s botanical notes, the daily entries of soldiers like Patrick Gass and Joseph Whitehouse — were not fully compiled and published in scholarly form until the University of Nebraska Press completed its monumental 13-volume edition, edited by Gary Moulton, in 2001.

What May 14, 1804, Teaches Us About Civic Leadership

The Lewis and Clark Expedition was a government-funded scientific and diplomatic mission — one of the first great exercises of federal power in the young republic. Jefferson used existing legal authority carefully, seeking congressional approval for funding before the Louisiana Purchase was even complete, and framing the expedition’s mandate in commercial and scientific terms that would justify the expenditure under the Constitution.

The expedition also illustrates both the promise and the profound moral failures of early American expansion. The Corps traveled through lands belonging to dozens of sovereign Native nations. While Lewis and Clark’s diplomatic conduct was often respectful by the standards of the era, the expedition ultimately served as the vanguard of westward expansion that would dispossess those nations of their homelands. York contributed throughout the journey yet received no land, no pay, and no immediate freedom. Sacagawea guided the Corps through the most difficult terrain of the journey and was indispensable to its survival — yet received no compensation and remains one of the most celebrated yet least-documented figures in American history.

A complete civics reading of May 14, 1804, holds both truths at once: a remarkable story of courage, scientific achievement, and national ambition — and a story that asks us to consider who bore the costs, and whose stories took longest to be told.

Timeline of the Corps of Discovery

May 2, 1803:  Louisiana Purchase finalized in Paris; the U.S. acquires ~828,000 square miles of western territory from France.
June 20, 1803:  Jefferson sends formal written instructions to Lewis defining the expedition’s objectives.
July 1803:  William Clark accepts Lewis’s invitation to co-lead; Clark recruits men in Kentucky while Lewis procures supplies.
December 1803:  Corps establishes Camp Dubois (Camp Wood) at the confluence of the Missouri and Mississippi rivers; winter training begins.
March 10, 1804:  Official transfer of Upper Louisiana from France to the United States clears the final diplomatic barrier.
May 14, 1804: ~4 PM  Clark and approximately 42 members of the Corps depart Camp Dubois. Clark’s journal: “The mouth of the River Dubois is to be considered as the point of departure.”
May 20–21, 1804:  Lewis joins the Corps at St. Charles, Missouri; the full expedition sets out together up the Missouri River.
August 20, 1804:  Sgt. Charles Floyd dies of a ruptured appendix — the only fatality of the entire expedition.
October–November 1804:  Corps reaches Mandan villages in present-day North Dakota; builds Fort Mandan for the winter.
February 11, 1805:  Sacagawea gives birth to Jean Baptiste Charbonneau at Fort Mandan.
April 7, 1805:  The permanent Corps of 33 departs Fort Mandan; a smaller group returns to St. Louis with specimens and reports.
August 12, 1805:  Lewis crosses the Continental Divide at Lemhi Pass — the first American to do so.
November 7, 1805:  Clark writes: “Ocean in view! O! the joy!” The Corps reaches the Pacific Ocean.
March 23, 1806:  Corps departs Fort Clatsop, Oregon, and begins the return journey east.
September 23, 1806:  The Corps of Discovery returns to St. Louis, completing a journey of approximately 8,000 miles in 28 months.

Sources & Further Reading

• [1]Constituting America, “May 14, 1804: Lewis and Clark Begin Exploration of the Missouri River” (James C. Clinger). constitutingamerica.org
• [2]Monticello (Thomas Jefferson Foundation), “Lewis and Clark: The Journey West.” monticello.org/lewis-and-clark/the-journey-west
• [3]History.com Editors, “Lewis and Clark Depart to Explore the Northwest,” HISTORY, May 14. history.com/this-day-in-history/may-14/lewis-and-clark-depart
• [4]National Park Service, Missouri National Recreational River, “The Lewis and Clark Expedition.” nps.gov/mnrr/learn/historyculture/the-lewis-and-clark-expedition.htm
• [5]Journals of the Lewis and Clark Expedition, University of Nebraska Press — May 14, 1804 entry. lewisandclarkjournals.unl.edu