Final answer:
President Jefferson appointed Meriwether Lewis, assisted by William Clark, to lead the Corps of Discovery and explore the western territories of the United States.
Step-by-step explanation:
President Jefferson chose his personal secretary, the army captain Meriwether Lewis, to lead the expedition to the west. Lewis, in collaboration with William Clark, formed the Corps of Discovery, with the objective of exploring the Louisiana territory that the United States had acquired through the Louisiana Purchase.
During their expedition from 1804 to 1806, Lewis and Clark aimed to map the territory, assess its commercial potential, explore trade routes, and document its geography, flora, and fauna.
Though the Northwest Passage they hoped to find did not exist, their monumental journey provided a significant contribution to the understanding of the American West.