The primary purpose of the Lewis and Clark expedition, which took place between 1804 and 1806, was to explore and map the newly acquired western portion of the United States following the Louisiana Purchase in 1803. Commissioned by President Thomas Jefferson, the expedition aimed to find a practical route to the Pacific Ocean, establish trade with Native American tribes, and gather scientific information about the region's flora, fauna, and geography. Meriwether Lewis and William Clark, along with their crew, provided valuable insights into the vast and largely uncharted territories of the American West.