In a splendid retelling of a great story, Ambrose chronicles Lewis and Clark's epic 1803-06 journey across the continent and back. Thomas Jefferson, more than anyone else, helped to effect the dream of a transcontinental US. As noted historian Ambrose (Univ. of New Orleans; D-Day, 1994, etc.) recounts, Jefferson's first great accomplishment in this regard was the Louisiana Purchase. His second was the dispatching of a US Army "Corps of Discovery" under his neighbor and friend, Captain Meriwether Lewis, to travel by land to the Pacific Ocean in search of a waterway to the West. Lewis, partner William Clark, and their 30-man expeditionary force recorded hundreds of species of birds, plants, and animals not previously known to Western science; mapped the interiors of the country; established ties with Indian tribes of the Northern Plains and the Northwest; and set the stage for the exploitation of the western country, particularly in the fur trade. Also, by Ambrose's account, Lewis and Clark's well-meaning ignorance and diplomatic maladroitness set the tone for early American relationships with Native Americans. Despite their close relationships with some Indians, Lewis and Clark persisted in absurd beliefs about them, some of which were subscribed to by Jefferson, as well (e.g., that Indians were descendants of a long-lost tribe of Welshmen). Although the expedition was a great success and fame and fortune followed, Lewis, now drinking heavily and suffering setbacks in love and politics, fell into a deep depression and committed suicide in 1809. The author speculates that he might have considered his great expedition a failure because the land remained unexploited by Americans. A fascinating glimpse of a pristine, vanished America and the beginning of the great and tragic conquest of the West.