The Lewis and Clark Expedition, also known as the Corps of Discovery Expedition, was a military and scientific journey commissioned by President Thomas Jefferson that lasted from May 14th, 1804, to September 23rd, 1806. It was led by Captain Meriwether Lewis and Second Lieutenant William Clark and covered nearly 8,000 miles in total. The expedition set out from St. Louis, Missouri, traveled westward up the Missouri River, crossed the Rocky Mountains, and followed the Columbia River to the Pacific Ocean before returning home. Its primary goals were to explore and map the territory acquired by the Louisiana Purchase, to find a practical water route across the continent to the Pacific, and to establish diplomatic relations and trade with the Native American peoples of the interior. The expedition was the first organized overland crossing of the North American continent by citizens of the United States and produced an enormous amount of scientific, geographical, and political knowledge that helped open the American West to further exploration and settlement.
What Was Westward Expansion?
Westward Expansion was the process by which the United States grew from its original boundaries along the eastern seaboard to eventually stretch across the entire North American continent to the Pacific Ocean. This expansion took place primarily during the 18th and 19th centuries and was driven by the belief known as Manifest Destiny, the idea that it was the inevitable right and duty of the United States to expand westward across the continent. The Lewis and Clark Expedition was one of the most important events in the history of American westward expansion, providing the first detailed knowledge of the vast interior of the continent and demonstrating that it was possible to travel overland from the Mississippi River to the Pacific Ocean.
Lewis and Clark Expedition – Background and Jefferson’s Goals
The Lewis and Clark Expedition grew directly out of the Louisiana Purchase of 1803, in which President Jefferson arranged the purchase of approximately 828,000 square miles of territory from France, doubling the size of the United States overnight. Even before the purchase was finalized, Jefferson had asked Congress in January of 1803 to fund an expedition to explore the interior of the continent. He had long been fascinated by the geography of North America and believed that a practical water route connecting the Missouri River to the Pacific Ocean might exist, which would open up trade with Asia and the Pacific coast.
Jefferson had several specific goals for the expedition. He wanted it to map the Missouri River and its tributaries. He wanted his explorers to make detailed scientific records of the plants, animals, geology, and climate of the region. He wanted them to study and record information about the Native American peoples they encountered, including their languages, customs, and political structures. He also wanted the expedition to establish friendly relations with Native American nations and lay the groundwork for future American trade in the region. Finally, by sending American explorers into the territory, Jefferson was asserting the United States’ claim to the region against the competing interests of Britain and Spain.
Lewis and Clark Expedition – Lewis, Clark, and the Corps of Discovery
Meriwether Lewis was a 29-year-old army captain who had served as Jefferson’s personal secretary and had significant experience in the frontier and military life. Jefferson personally selected him to lead the expedition. Lewis invited his close friend William Clark, a 33-year-old former army officer with experience in frontier warfare and mapmaking, to co-command the expedition. The two men complemented each other well, with Lewis tending toward scientific observation and Clark toward mapmaking and managing relations with Native peoples.
The party they assembled, known as the Corps of Discovery, included approximately 45 men in its initial form, though only about 33 traveled the full route to the Pacific and back. The members included army soldiers, frontiersmen, hunters, and interpreters. Among them was York, an enslaved African American man belonging to Clark who traveled the entire route and whose presence proved significant in relations with Native peoples, many of whom had never seen a Black person before. Jefferson commissioned Lewis as a captain and granted Clark the equivalent rank in practice, though the army officially gave Clark the lower rank of second lieutenant, something Lewis considered an injustice and largely ignored in practice.
Lewis and Clark Expedition – The Journey West
The expedition set out from Camp Dubois in Illinois on May 14th, 1804, and traveled to St. Charles, Missouri, where they picked up Lewis and additional members. They then headed up the Missouri River by boat, traveling in a large keelboat and two smaller dugout boats called pirogues. Progress was slow but steady, covering 10 to 20 miles per day against the strong Missouri current. The party traveled through what is now Missouri, Kansas, Nebraska, Iowa, and South Dakota, making contact with numerous Native American nations along the way including the Oto, Missouri, Yankton Sioux, and Teton Sioux.
As autumn approached, the expedition reached the Mandan and Hidatsa villages near present-day Bismarck, North Dakota, where they decided to spend the winter. They built a small fort they named Fort Mandan and settled in for the cold months. During the winter at Fort Mandan, Lewis and Clark met two people who would prove crucial to the success of their journey. Toussaint Charbonneau was a French-Canadian fur trapper living among the Mandan people. His young wife was a Shoshone woman named Sacagawea, who had been kidnapped from her people as a child and sold to Charbonneau. Lewis and Clark hired Charbonneau as an interpreter and allowed Sacagawea to accompany the expedition. On February 11th, 1805, Sacagawea gave birth to a son, Jean Baptiste, just weeks before the expedition was to resume. The baby traveled with his mother for the entire journey.
On April 7th, 1805, the expedition resumed its westward journey with 33 people, having sent the keelboat back to St. Louis with a collection of scientific specimens, maps, and reports for Jefferson. The party traveled up the Missouri River through what is now Montana, navigating around the Great Falls of the Missouri in June of 1805, a portage that took nearly three weeks to complete. At the Three Forks of the Missouri River in August, Sacagawea recognized the area as the homeland of her Shoshone people. Lewis went ahead and made contact with a Shoshone band, and in one of the most remarkable coincidences of the entire journey, Sacagawea discovered that the band was led by her own brother Cameahwait. She was reunited with her family after years of separation. The Shoshone provided the expedition with horses and a guide, a man called Old Toby, who led them through the Bitterroot Mountains.
The crossing of the Bitterroot Range was the most grueling part of the entire journey. The mountains were steeper and more extensive than anyone had anticipated, and by the time the party descended into the territory of the Nez Perce people in September of 1805, they were exhausted, half-starved, and suffering from exposure. The Nez Perce treated them generously, fed them, and helped them build canoes to continue westward by river. The expedition followed the Clearwater, Snake, and Columbia Rivers westward through present-day Idaho, Washington, and Oregon. On November 7th, 1805, Clark wrote in his journal the famous words Ocian in view, O the joy, when the party caught their first glimpse of the Pacific Ocean. They spent the winter at Fort Clatsop, a small post they built south of the Columbia River near present-day Astoria, Oregon.
Lewis and Clark Expedition – Sacagawea
Sacagawea played an essential role in the success of the expedition that went far beyond her formal role as an interpreter. Her presence with the group served as a powerful signal to Native peoples that the expedition was peaceful in its intentions, since war parties in Native American culture did not travel with women and children. In fact, Lewis and Clark noted repeatedly that Sacagawea’s presence helped defuse potentially hostile encounters with Native peoples who might otherwise have viewed the expedition with suspicion.
She also contributed directly to the expedition’s survival in multiple ways. She identified edible plants and roots when food was scarce, helped obtain horses from the Shoshone that were essential for crossing the mountains, and used her knowledge of the landscape to guide the party in her home territory. Her reunion with her brother and the Shoshone people came at a critical moment when the expedition desperately needed horses and guidance through the mountains, and it is widely accepted by historians that without Sacagawea’s contribution the expedition would have struggled far more seriously and might not have succeeded.
Lewis and Clark Expedition – The Return Journey
The Corps of Discovery began its return journey on March 23rd, 1806, traveling back up the Columbia River and eventually over the mountains. To explore more of the territory, Lewis and Clark split the party into two groups east of the Continental Divide. Lewis took a shortcut north through the Great Falls region and explored the Marias River, while Clark led his group south along the Yellowstone River. The two groups reunited at the confluence of the Yellowstone and Missouri Rivers on August 12th, 1806.
The expedition returned Sacagawea, Charbonneau, and their son to the Mandan villages and then traveled rapidly down the Missouri River with the current in their favor, covering 70 or more miles per day. They arrived in St. Louis on September 23rd, 1806, to a hero’s welcome. They had been gone two years and four months. Jefferson greeted them as national heroes upon their return to Washington. Lewis was appointed governor of the Louisiana Territory and Clark was named Indian agent for the West.
Lewis and Clark Expedition – Results and Discoveries
The Lewis and Clark Expedition produced an extraordinary amount of new knowledge about the interior of North America. Lewis and Clark created approximately 140 detailed maps of the regions they traveled through, mapping mountain ranges, rivers, and plains that had previously been unknown to Americans. Lewis identified 178 plant species and 122 animal species previously unknown to science, including the prairie dog, the pronghorn antelope, the grizzly bear, and the California condor. The expedition made detailed notes on the geography, climate, and natural resources of the vast territory through which it traveled.
The Corps of Discovery also made contact with more than two dozen Native American nations during the journey, establishing peaceful relations with most of them and gathering valuable information about their cultures, languages, and territories. In fact, the expedition was notably peaceful, with only one violent incident of any significance occurring during the entire journey. Despite failing to find the hoped-for continuous water route to the Pacific, the expedition demonstrated that an overland crossing of the continent was possible and provided the maps and knowledge that would guide the next generation of American explorers and settlers moving west.
Lewis and Clark Expedition – Significance
The significance of the Lewis and Clark Expedition in the history of American westward expansion is enormous. Most immediately, it provided the United States government with the detailed geographical knowledge needed to understand and administer the vast territory of the Louisiana Purchase. The maps, journals, and scientific specimens Lewis and Clark brought back gave Americans their first real picture of the interior of the continent and dispelled the myth that a practical water route to the Pacific existed.
The expedition also strengthened the American claim to the Oregon Country, the Pacific Northwest region that was at the time disputed between the United States and Britain. The presence of American explorers and the detailed records they kept helped establish an American claim to the region that eventually led to the Oregon Territory being incorporated into the United States in 1846.
Most broadly, the Lewis and Clark Expedition opened the American West to the imagination of the American people. After hearing of the expedition’s success, migration westward accelerated significantly. The routes, peoples, and landscapes Lewis and Clark had documented provided the knowledge base for the wave of settlement that would transform the American interior over the following decades. As such, the Lewis and Clark Expedition stands as one of the most significant and consequential journeys in the history of the United States.
