Thomas Jefferson commissioned Meriwether Lewis to lead an expedition to explore the newly acquired Louisiana Territory and report back on plant and animal life and opportunities for trade. Lewis chose William Clark as co-leader of the Corps of Discovery expedition. Starting in 1804, their journey lasted over two years, covering over 7,500 miles to the Pacific Ocean and back. A key stop was the confluence of the Snake and Columbia Rivers in present-day Washington, where they camped for two nights and met over 200 Native Americans.