The importance of the Lewis and Clark Expedition, which took place from 1804 to 1806, lies in its role in American expansion and exploration. Commissioned by President Thomas Jefferson, the expedition aimed to explore the newly acquired Louisiana Territory and find a water route to the Pacific Ocean. Led by Meriwether Lewis and William Clark, the journey provided valuable information about the geography, resources, and indigenous cultures of the western lands. Its findings encouraged westward migration and laid the groundwork for the United States' growth, manifesting the idea of Manifest Destiny.