[Simon & Schuster] From the New York Times bestselling author of Band of Brothers and D-Day, the definitive book on Lewis and Clark’s exploration of the Louisiana Purchase, the most momentous expedition in American history and one of the great adventure stories of all time. 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 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 vivid backdrop for the expedition. Lewis is supported by a rich variety of colorful characters, fir