The Louisiana Purchase and the Corps of Discovery

In 1803, President Thomas Jefferson faced an awkward problem: he believed in strict construction, and the Constitution said nothing about the President buying land from a foreign country -- yet France's Napoleon Bonaparte had just offered to sell the entire Louisiana Territory, roughly 828,000 square miles stretching from the Mississippi River to the Rocky Mountains, for about $15 million. Jefferson decided the deal was too good to pass up and stretched his own principles to complete the Louisiana Purchase, instantly doubling the size of the United States.

To learn what the new territory actually contained, Jefferson sent the Corps of Discovery, led by Meriwether Lewis and William Clark, on a roughly 8,000-mile round-trip expedition from 1804 to 1806, mapping the land, recording plants and animals, and making contact with dozens of Native nations along the way. Two members proved essential to the mission's success: Sacagawea, a young Shoshone woman, served as a guide and interpreter and helped the expedition negotiate safely through Native territories, and York, an enslaved man owned by Clark, worked as a full member of the expedition -- hunting, scouting, and voting alongside everyone else on group decisions, even though he would not be granted his own freedom until years after returning.