The main purpose of the Lewis and Clark expedition, which took place from 1804 to 1806, was to explore the newly acquired Louisiana Territory following the Louisiana Purchase in 1803. Commissioned by President Thomas Jefferson, the expedition aimed to map the territory, establish trade relations with Indigenous tribes, search for a Northwest Passage to the Pacific Ocean, and gather scientific information about the land's flora, fauna, and geology. Led by Meriwether Lewis and William Clark, the journey provided valuable insights into the geography and natural resources of the American West and helped to pave the way for further westward expansion.