Which explorer did Thomas Jefferson appoint to lead the Corps of Discovery expedition?

Thomas Jefferson appointed Meriwether Lewis to lead the Corps of Discovery expedition.

The expedition began in 1804, soon after the Louisiana Purchase, to explore the newly acquired territory and find a practical route across the continent. Lewis was Jefferson’s private secretary and had military experience, natural-history interests, and familiarity with frontier conditions.

Lewis invited William Clark to serve as a co-leader. Although Lewis held the formal commission as captain, Clark was also an experienced Army officer and surveyor. The partnership became the expedition’s defining leadership arrangement, which is why the journey is commonly called the Lewis and Clark Expedition.

The party traveled from the Missouri River to the Pacific coast and back between 1804 and 1806. Sacagawea, a Lemhi Shoshone woman, joined the expedition with her husband Toussaint Charbonneau and helped with communication and navigation. The expedition did not discover a direct water route across the continent, but it mapped major regions and recorded extensive information about their geography, plants, animals, and peoples.