The Louisiana Purchase in 1803 nearly doubled the size of the United States. The U.S. suddenly went from consisting of 17 states along the Atlantic coast to claiming land as far west as present-day Montana. The U.S. government knew little about the terrain there. Was there a water route to the Pacific? President Thomas Jefferson sent William Clark and Meriwether Lewis to find out. With nothing to guide them but a compass, what would Lewis and Clark discover? Readers will find the answer to this question and how an artifact can tell us about U.S. history.