The primary mission of the Lewis and Clark Expedition, which took place from 1804 to 1806, was to explore the newly acquired western territories 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 conduct scientific research. Meriwether Lewis and William Clark led the expedition, mapping the terrain, collecting flora and fauna, and documenting their interactions with various indigenous peoples. Their journey greatly enhanced American knowledge of the west and set the stage for further exploration and settlement.