In January of 1803, President Thomas Jefferson sent a secret message to Congress, requesting $2,500 to fund an exploration of the West all the way to the Pacific Ocean. By year's end, the Louisiana Purchase had doubled America's size, and what started in secrecy became the nation's greatest news. The Lewis and Clark expedition departed in May 1804 and returned in September 1806, having mapped 8,000 miles of continent.

Key Takeaways

• Jefferson initially requested just $2,500 for the expedition, in secret, since the U.S. didn't yet own the land west of the Mississippi

• The Louisiana Purchase (1803) doubled America's size and turned the secret mission into a national undertaking

• Sacagawea, a Shoshone woman, joined the Corps of Discovery at Fort Mandan (North Dakota) and proved essential as interpreter and guide

• Clark captured the moment of reaching the Pacific: 'Ocean in view. Oh, the joy.'

• Only one man died on the entire expedition (Sergeant Charles Floyd); the vote on where to winter included an Indian, a Black man, and a woman

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FAQ - Frequently Asked Questions

Q1: Why did Jefferson keep the Lewis and Clark expedition secret at first?

When Jefferson requested $2,500 from Congress in January 1803, the United States did not yet own any land west of the Mississippi River. Proposing to explore territory that technically belonged to France required discretion. By year's end, the Louisiana Purchase had doubled the size of the country and removed the need for secrecy, what began as a covert mission became a celebrated national undertaking.

Q2: Who was Sacagawea and why was she important to the expedition?

Sacagawea was a Shoshone woman who joined the Corps of Discovery at Fort Mandan in North Dakota in the winter of 1804–1805. She was six months pregnant when she joined; her son Jean Baptiste was born that winter. Her knowledge of the terrain and Native American languages proved crucial throughout the journey. Her presence with an infant also made the expedition appear peaceful to tribes they encountered. She helped acquire horses from the Shoshone, which allowed the Corps to cross the Bitterroot Mountains.

Q3: What did Lewis and Clark actually accomplish?

The Corps of Discovery traveled roughly 8,000 miles over more than two years, mapping the western territory from St. Louis to the Pacific Ocean. They documented plant and animal species previously unknown to science, including the grizzly bear, prairie dogs, and bighorn sheep, and made contact with dozens of Native American tribes. Though they did not find a continuous water route to the Pacific, they vastly expanded American knowledge of the West and inspired generations of westward migration.

A Secret Message and a Historic Purchase

In January of 1803, President Thomas Jefferson sent a secret message to Congress. He requested $2,500 for the purpose of funding an exploration of the West. The proposed expedition would go all the way to the Pacific Ocean. At the time, the United States did not own any land west of the Mississippi, hence the need for secrecy. Circumstances changed dramatically, however, by the end of the year when Jefferson's envoys to France ended up purchasing the Louisiana Territory. Then what started in secrecy became the nation's greatest news. The Lewis and Clark expedition reached St. Louis on September 23rd, 1806, after more than two years of exploration. Three months later, on December 28th, Lewis arrived triumphantly in Washington, D.C., followed by Clark in January. No less than the entire nation was waiting to hear and see what they had found. By the end of 1803, there was no more need for Jefferson's initial secrecy. In December that year, the entire territory of Louisiana was transferred to the United States under a purchase agreement negotiated with French consul Napoleon Bonaparte.

America was now nearly twice the size it was at the beginning of that year. Jefferson left no time to waste. He commissioned the expedition officially known as the Corps of Discovery. Led by Meriwether Lewis and William Clark, the expedition aimed to explore and map the vast lands of the West. For centuries, statesmen and explorers had sought a northwest passage to the Orient. Jefferson wondered if there just might be a route entirely navigable by water all the way across the continent. The key would be a connection between the Missouri and Columbia rivers. Additionally, the expedition was to study the area's natural resources and indigenous peoples. The territory Lewis and Clark were sent to map had only just been acquired, as we cover in our episode on the Louisiana Purchase.

Departure and the Journey West

The official leader of the Corps was Captain Lewis. The United States Secretary of War, Henry Dearborn, turned Lewis down when he requested that Clark share his command. But while Clark was a second lieutenant, he and Lewis addressed each other as captain and never revealed to the rest of the expedition what Dearborn had dictated. On May 14th, 1804, the expedition departed from near St. Louis, Missouri. Their primary vessel was a 55-foot keelboat, accompanied by two smaller pirogues. The initial leg of their journey took them up the Missouri River against the current. A pivotal moment in the expedition occurred in November 1804 when they established Fort Mandan in present-day North Dakota and stayed there for the winter. Here they met Sacagawea, a Shoshone woman who would become an invaluable interpreter and guide for the Corps. She was married to French-Canadian trapper Toussaint Charbonneau, who also joined the expedition. Sacagawea was six months pregnant.

Their son Jean Baptiste was born that winter of 1805. Her knowledge of the terrain and Native American languages would prove crucial. When native tribes saw her with her infant, the entire expedition appeared more peaceful to them. The native peoples they encountered had occupied the land for thousands of years, as we cover in our episode on the first Americans.

The Rockies and the Pacific

In the spring of 1805, the Corps of Discovery continued their westward push, navigating the treacherous Great Falls of the Missouri. The Rocky Mountains presented the most significant geographical barrier. With Sacagawea's assistance, they acquired horses from the Shoshone and successfully traveled over the Bitterroot Mountains, a grueling journey marked by hunger and harsh conditions. Upon reaching the Clearwater River, they constructed canoes and began their descent toward the Pacific. They followed the Snake River to the Columbia River, reaching the Pacific Ocean in November 1805. Clark captured the moment in his journal: "Ocean in view. Oh, the joy." The Corps erected Fort Clatsop near present-day Astoria, Oregon, where they spent the winter of 1805–1806. The decision to stay there through the winter months was the result of an unprecedented referendum. Lewis and Clark put the matter to a vote. Among the voters were an Indian, a Black man, and a woman.

The Return and the Legacy

Lewis and Clark returned to St. Louis in September 1806. The journey west plus the return trip amounted to 8,000 miles of travel in total. The expedition had lasted more than two years. Only one man died on the entire expedition: Sergeant Charles Floyd. The Corps of Discovery successfully mapped the western territory, collecting invaluable data on its geography, plant life, and animal species, including the grizzly bear, prairie dogs, and bighorn sheep. They established contact with numerous Native American tribes: the Mandan, Hidatsa, Shoshone, Nez Perce, Sioux, Cheyenne, Crow, Blackfeet, Chinook, Clatsop, and Walla Walla.

Although they did not find a continuous water route to the Pacific, they greatly expanded American knowledge of the West. They also greatly inspired American expansion into the West, thereby shaping the century to come. The Oregon Trail, which thousands of settlers would travel in the 1840s, followed routes that Lewis and Clark had mapped. Conflict with native nations on the western frontier would continue for decades, as we cover in our episode on Tecumseh, Harrison, and the Battle of Tippecanoe.