The Lewis and Clark Expedition (1804–1806) was a federally funded venture to explore the North American West. The expedition’s principal objective was to survey the Missouri and Columbia rivers, locating routes that would connect the continental interior to the Pacific Ocean. Theof 1803, in which the United States acquired some 828,000 square miles of land west of the Mississippi River, facilitated the mission, allowing the explorers unprecedented access to land that had previously been owned by Spain and then France. President invested his time, energy, and political capital into this project and took direct charge of its initial planning and organization. The expedition is named for its commanders, Meriwether Lewis and William Clark. Under their leadership the group of thirty-three, known as the Corps of Discovery, succeeded in reaching the Pacific and returning safely despite considerable challenges, ranging from navigating unfamiliar terrain to maintaining good relations with the numerous Indian tribes that lived in the Louisiana Territory. Along the way, the expedition gathered invaluable scientific, ethnographic, and cartographic information, creating a detailed written record of the journey in a series of journals.