Missouri marked both the beginning and the end of the Lewis and Clark Expedition, which followed the United States' acquisition of the Louisiana Territory in St. Louis in March 1804 and set out two months later up the Missouri River toward the Pacific in hopes of opening a new American era of trade, diplomacy, and settlement. After wintering at Camp River DuBois and making a final recruiting stop in St. Charles, the Corps of Discovery began with 45 members, including army sergeants and privates, Clark's slave York, a French-Shawnee interpreter, and French-Canadian, French-Omaha, and French-Missouri Indian boatmen. On the westward journey, the expedition spent 66 days in what is now Missouri, struggling against the swift and dangerous Missouri River in a poorly suited 55-foot keelboat and two pirogues as the crew contended with snags, sandbars, driftwood, collapsing banks, broken masts and towropes, heat, sand, mosquitoes, and exhaustion, yet repeatedly avoided disaster through determined collective effort. Along the way, the party encountered fur traders, signs of Indian war parties, and Indian pictographs, and the journal keepers recorded Missouri's forests, bluffs, prairies, caves, creeks, and springs as the landscape changed from wooded eastern country to western prairie. The expedition's return to St. Louis in 1806 ended hopes for a Northwest Passage, but after crossing the Rocky Mountains and reaching the Pacific, Lewis and Clark had met nearly 50 Indian nations, compiled extensive scientific records including 300 previously undescribed plants and animals, become 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.