Undaunted Courage: Meriwether Lewis, Thomas Jefferson, and the Opening of the American West (ISBN 0684811073), written by Stephen Ambrose, is a 1996 biography of Meriwether Lewis of the Lewis and Clark Expedition. The book is based on journals and letters written by Lewis, William Clark, Thomas Jefferson and the members of the Corps of Discovery. While most of the book is dedicated to the expedition, several chapters are also devoted to Lewis's early life as a Virginia planter and Jefferson's personal secretary, and his later life as governor of the Louisiana Territory before his untimely death in 1809.