The Journals of Lewis and ClarkBy: Meriwether Lewis, William Clark In 1803, when the United States purchased Louisiana from France, the great expanse of this new American territory was a blanknot only on the map but in our knowledge. President Thomas Jefferson keenly understood that the course of the nation's destiny lay westward and that a national "Voyage of Discovery" must be mounted to determine the nature and accessibility of the frontier. He commissioned his young secretary,