In 1803 President Thomas Jefferson selected his personal secretary, Captain Meriwether Lewis, to lead a voyage up the Missouri River to the Rockies, over the mountains, down the Columbia River to the Pacific Ocean, and back. Lewis was the perfect choice. He endured incredible hardships and saw incredible sights, including vast herds of buffalo and Indian tribes that had had no previous contact with white men. He and his partner, Captain William Clark, made the first map of the trans-Mississippi West, provided invaluable scientific data on the flora and fauna of the Louisiana Purchase territory, and established the American claim to Oregon, Washington, and Idaho. Ambrose has pieced together previously unknown information about weather, terrain, and medical knowledge at the time to provide a colorful and realistic backdrop for the expedition. Lewis saw the North American continent before any other white man; Ambrose describes in detail native peoples, weather, landscape, science, everything the expedition enc