From 1804 to 1806, Captains Meriwether Lewis and William Clark led the Corps of Discovery on a journey ordered by President Thomas Jefferson to find a water route to the Pacific Ocean through the newly acquired Louisiana territory. During the expedition, they mapped the land, recorded its resources, and met with and learned from its native inhabitants. In preparation, Meriwether Lewis studied medicine, botany, zoology, and celestial observation, and with Jefferson's permission asked his friend and former commanding officer William Clark to serve as co-leader. Clark contributed his abilities as an outdoorsman, geographer, and map-maker, and though the two men had opposite temperaments, they worked harmoniously throughout the two-year journey.