First Across the Continent

'First Across the Continent' is a book that covers the Lewis and Clark Expedition, which is also known as the Corps of Discovery Expedition. It was a United States expedition to cross the newly acquired western portion of the country after the Louisiana Purchase. The Corps of Discovery was a select group of U.S. Army and civilian volunteers under the command of Captain Meriwether Lewis and his close friend Second Lieutenant William Clark. President Thomas Jefferson commissioned the expedition shortly after the Louisiana Purchase to explore and to map the newly acquired territory, to find a practical route across the western half of the continent, and to establish an American presence in this territory before European powers attempted to establish claims in the region.