In 1803, the United States purchased the Louisiana Territory from France, expanding the country from the Mississippi River west to the Rocky Mountains and from the Gulf of Mexico north to Canada. President Thomas Jefferson recognized that American settlers would soon cross the Mississippi River into the unmapped West known only to the American Indians, and the need for knowledge of that West and for a water route that could carry American commerce across the continent drove his request to Congress for funds for an exploratory expedition to the Pacific Ocean. Jefferson appointed 29-year-old Captain Meriwether Lewis to lead the Corps of Discovery from Wood River, Illinois, near St. Louis, Missouri, to the Pacific Ocean at the mouth of the Columbia River, and Lewis chose his 33-year-old friend William Clark, under whom he had served in the Army, as co-leader. After more than two years crossing North America, they returned with documented accounts of their travels and observations in the Journals of the Lewis and Clark Expedition, which recorded mileage, described mountains, rivers, climates, flora, and fauna, and detailed contacts with the peoples living on the plains, in mountain valleys, and along river shores. The expedition became an epic event in American history, turning the West from a place of fantasy and imagination into one of reality and possibility that established a vision of an American future.