On the afternoon of May 14, 1804, a keelboat and two smaller boats pushed off from a muddy camp in Illinois called Camp Dubois. Nobody waved them off into history that day — they were simply thirty-some men heading up the Missouri River, following orders. They had no idea what lay ahead, how long the trip would take, or whether they would return at all. What they carried with them, though, tells its own story: 193 pounds of portable soup, mosquito netting, medical supplies, and a repeating air rifle powerful enough to drop a deer. This was not a casual outing. It was the first American attempt to see, measure, and claim a continent.
A President’s Curiosity, and a Race Against Rivals
Thomas Jefferson had been fascinated by the unexplored West for decades before he ever had the power to do anything about it. While serving as Minister to France in the 1780s, he discussed a possible Pacific expedition with the adventurer John Ledyard. He had also read Captain James Cook’s account of his third voyage and a history of Louisiana by Le Page du Pratz — both of which shaped his thinking about what might lie beyond the Mississippi. Jefferson wanted what Cook had wanted: a practical route to the Pacific.
There was urgency behind the curiosity. The British explorer Alexander Mackenzie had already crossed the continent to the Pacific coast of British Columbia in 1793, a dozen years before Lewis and Clark would manage the same feat farther south. Mackenzie’s published account made clear that Britain intended to dominate the fur trade along the Columbia River. For Jefferson, this was a warning. If the United States didn’t establish a presence in the West soon, someone else would claim it first.
So in 1803, shortly after the Louisiana Purchase had roughly doubled the size of the country on paper, Jefferson asked Congress to fund an expedition. He was not entirely open about his reasons — poor relations with the opposition Federalist Party led him to request the funding through a secret message rather than a public appeal. Congress approved $2,324, modest money for a mission meant to cross a continent, and put it in the hands of a young Army captain named Meriwether Lewis.
Building the Corps
Jefferson’s choice of Lewis was deliberate and, in his own words, almost impossible to replicate. He wanted someone who combined scientific knowledge — botany, astronomy, mineralogy, natural history — with the toughness of a frontiersman and some familiarity with Native American customs. Lewis had the second set of qualities already. The first set, Jefferson decided to teach him.
In 1803, Lewis was sent to Philadelphia for a crash course in exploration science. Benjamin Rush, the physician and Revolutionary War figure, taught him medicinal cures. Andrew Ellicott instructed him in using a sextant and other navigational tools. Benjamin Smith Barton showed him how to describe and preserve plant and animal specimens, while Robert Patterson refined his skills in calculating latitude and longitude. Caspar Wistar briefed him on fossils. Lewis also had the run of Jefferson’s immense personal library at Monticello, full of maps and accounts of North American geography. He was, by the time he set out, about as well-prepared an amateur scientist as the era could produce.
Lewis chose William Clark, a close friend, to co-lead the expedition. The two men assembled what became known as the Corps of Discovery — by some accounts as many as 45 people, including Army officers and enlisted men, civilian volunteers, and York, an African-American man enslaved by Clark. A Newfoundland dog named Seaman joined them too, purchased by Lewis in Pittsburgh, where the expedition’s keelboat had been built that summer to Lewis’s own specifications. Seaman would prove useful for hunting and guarding against predators, and he was the only animal to complete the entire journey.
Jefferson’s written instructions to the men were specific: find a water route — via the Missouri, and whichever river connected to it, whether the Columbia, the Colorado, or another — that could carry commerce across the continent to the Pacific. The expedition also carried Indian Peace Medals, silver medallions bearing Jefferson’s portrait, meant to be handed out as gestures of friendship to the tribes they encountered. They carried flintlock firearms and an Austrian air rifle too, a none-too-subtle display of American firepower alongside the diplomacy.
Up the Missouri
Clark led the first leg out of Camp Dubois on May 14, 1804, traveling the keelboat and two pirogues up the Missouri to St. Charles, Missouri. Lewis caught up with the group six days later, and the full expedition finally got underway on May 21. From St. Charles they followed the river through territory that is now Kansas City and Omaha, pushing into country thick with elk, deer, bison, pronghorn, and beaver as they reached the edge of the Great Plains in late August.
That same month brought the expedition’s only death. Sergeant Charles Floyd, one of the first men to sign on, died on August 20, 1804, apparently of acute appendicitis — a condition no frontier remedy could have treated. He was buried on a bluff overlooking the river, a site that still bears his name near present-day Sioux City, Iowa. His comrades marked the grave with a cedar post inscribed with his name and the date, then camped a mile upriver at a small stream they named in his honor.
The expedition’s survival depended less on its own supplies than on the goodwill of the people whose land it was crossing. Lewis and Clark established relations with roughly two dozen Native American nations along the way, and without that help, the Corps risked starving through brutal winters or losing themselves entirely in the Rocky Mountains. Not every encounter was friendly. Near the confluence of the Missouri and Bad rivers, in what is now Fort Pierre, South Dakota, the Corps met the Lakota — a nation the Americans called the Sioux, and one that other river travelers had already warned them about as powerful and determined to control trade on the Missouri. The Lakota were also bracing for retaliation after a raid against the Omaha tribe had killed 75 men and burned 40 lodges.
Tensions boiled over when one of the expedition’s horses went missing and the Americans suspected Lakota involvement. A tense standoff followed — demands for gifts or tribute, refusals, and several moments that came close to violence. Clark described the Lakota in his journal as “warlike” and used far harsher language besides. It was the Lakota chief Black Buffalo who ultimately defused the crisis, persuading Lewis to hand over more tobacco rather than let the confrontation turn deadly.
From there the expedition pressed on toward the Continental Divide near Lemhi Pass, eventually reaching the Columbia River and the Pacific Ocean in 1805. The return journey began at Fort Clatsop, Oregon, on March 23, 1806, and the Corps finally made it back six months later, on September 23, 1806, carrying journals, maps, and sketches for Jefferson back in St. Louis.
What we still don’t know
Some threads of the expedition’s story remain genuinely unsettled. Historians still debate how much Jefferson’s interest in gathering scientific data was driven by pure curiosity versus a calculated bid to strengthen the United States’ legal claim to the Pacific Northwest. The expedition’s chosen route may also owe something to a far older and disputed source: a secondhand account of a transcontinental journey supposedly made a century earlier by a Native traveler named Moncacht-Apé, recorded in Le Page du Pratz’s history of Louisiana. Lewis carried a copy of that book, and its vague description of the route — one that conveniently skips over the Rocky Mountains — may explain why the Corps mistakenly believed they could simply carry their boats overland from the Missouri’s headwaters to a westward-flowing Columbia. Reality, as they discovered, was considerably more mountainous than that.
Sources
– This article is a synthesis of the Wikipedia article on Lewis and Clark Expedition (en.wikipedia.org/wiki/Lewis_and_Clark_Expedition), which itself cites the underlying scholarship. Readers wanting primary sources should follow that article’s reference list.