Missouri was both the beginning and the end of the Lewis and Clark Expedition, a keystone American event planned by President Thomas Jefferson and carried out by Meriwether Lewis, William Clark, and their crew after the United States took ownership of the Louisiana Territory in St. Louis in March 1804. Two months later, the Corps of Discovery left winter camp at Wood River, made a final recruiting stop in St. Charles, and began moving up the Missouri River toward the Pacific in hopes of opening a new American era in trade, diplomacy, and settlement. With 45 members at the start, including army sergeants and privates, Clark's slave York, a French-Shawnee interpreter, and French-Canadian, French-Omaha, and French-Missouri Indian boatmen, the expedition spent 66 days in what is now Missouri on the westward journey and covered the same 600 miles in about two weeks when returning to St. Louis in 1806. In Missouri during the spring and summer of 1804, the river itself dominated the journey, as the 55-foot keelboat and two pirogues struggled against swift current, snags, moving sandbars, driftwood, collapsing banks, heat, sand, mosquitoes, broken masts, and worn towropes, yet repeated dangers were avoided through the crew's extraordinary exertions and shared determination. The travelers also encountered fur traders, signs of Indian war parties, and Indian pictographs on bluffs, while their journals recorded the forests, bluffs, prairies, caves, creeks, springs, and the transition from well-timbered eastern Missouri to the beautiful prairie farther west. When the expedition returned to St. Louis in 1806, it had ended the dream of a Northwest Passage, having reached the Pacific only after a hard crossing of the Rocky Mountains. During the full journey, Lewis and Clark met nearly 50 Indian nations, compiled extensive scientific observations, returned with records of 300 animals and plants not previously described, became the first Euro-American explorers to ascend the full length of the Missouri River from its mouth to its source, explored a large portion of the Columbia River, and helped establish a U.S. claim to the Pacific coast.