Jefferson and the Louisiana Purchase

Jefferson believed in strict construction: the federal government could only do what the Constitution explicitly said. Nothing in it mentions buying foreign land. But in 1803 Napoleon offered the entire Louisiana Territory, roughly 828,000 square miles stretching from the Mississippi River to the Rocky Mountains, from the Gulf of Mexico up into Canada, for fifteen million dollars. Jefferson wanted New Orleans to secure Mississippi River trade for Western farmers; Napoleon offered the whole territory instead. Jefferson swallowed his constitutional doubts, reasoned that treaty-making power covered it, and sent the deal to the Senate rather than risk losing it.

Napoleon sold for his own reasons. He had planned to use Louisiana to supply a renewed French empire centered on the sugar colony of Saint-Domingue, Haiti. A massive slave revolt there, led eventually to Haitian independence in 1804, destroyed thousands of French troops and the plan with them. With Haiti lost and war with Britain looming, Napoleon needed cash more than he needed a distant, costly territory, so he sold all of Louisiana rather than defend it.

To map and justify the purchase, Jefferson sent Meriwether Lewis and William Clark west in 1804. They left St. Louis, followed the Missouri River, crossed the Rockies with Shoshone guide Sacagawea's help, reached the Pacific near the Columbia River in 1805, and returned to St. Louis by 1806. Their reports of fertile land, rivers, and native nations fed the next decades of westward expansion and the arguments over slavery that came with it.