In 1803, when the United States purchased the Louisiana Territory from France (for a scant $15 million), it doubled the size of the young country. Stretching north from New Orleans to the Canadian border and westward from the Mississippi River to the Rocky Mountains, the area contained over 800,000 square miles. That same year, President Thomas Jefferson designated two young men — Meriweather Lewis and William Clark — as leaders of an expedition to explore this vast new...
