The Lewis & Clark Expedition: Route, Purpose & Legacy (1804–1806)

The Corps of Discovery (1804–1806) was the United States' first transcontinental scientific expedition—authorized by Jefferson, led by Meriwether Lewis and William Clark, and enabled by the Louisiana Purchase.

Route Overview

1. Camp Dubois, IL (winter 1803–04) → Missouri River
2. Up the Missouri to Mandan/Hidatsa villages (ND) — winter 1804–05
3. Westward: Montana (Great Falls portage), Rocky Mountains (Lemhi Pass)
4. Salmon River → Clearwater → Snake → Columbia to Pacific (Nov 1805)
5. Fort Clatsop, OR (winter 1805–06)
6. Return: Split parties (Lewis: Marias River; Clark: Yellowstone) → reunite in ND → St. Louis (Sept 1806)

Core Achievements

• Mapping: ~4,000 miles surveyed; first accurate Missouri/Columbia hydrography.
• Science: 178 plants, 122 animals new to science documented.
• Diplomacy: Councils with 50+ tribes; peace medals, trade promises.
• Sacagawea: Shoshone interpreter/guide—critical for horses, passage, trust.
• York: Clark's enslaved man; full participant, voted on decisions—remarkable for era.

Legacy

• Opened Oregon Trail, fur trade, US claim to Oregon Country.
• Scientific specimens founded early US natural history collections.
• Journals (1M+ words) remain primary source on pre-settlement West.

They didn't "discover" the West—Indigenous nations knew it intimately. They mapped it for the US empire.