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 during a ceremony in St. Louis in March 1804, the nation doubled in size and expansion to the Pacific Ocean seemed possible. Two months later, the Corps of Discovery departed, making a final recruiting stop in St. Charles in May 1804 before heading up the Missouri River toward the Pacific. 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 traveling through what is now Missouri on the westward journey and covered the same 600 miles in only two weeks on the return to St. Louis in 1806. The Missouri River dominated the early trip, as the 55-foot keelboat and two smaller pirogues struggled against swift current, snags, moving sandbars, driftwood, collapsing banks, heat, sand, mosquitoes, and repeated equipment failures, forcing the crew at times to tow the boat from shore. Yet these hardships drew the party together in a determined effort to succeed. Along the way, the expedition passed final settlements, met traders, observed Indian pictographs and signs of war parties, explored caves, creeks, springs, forests, bluffs, and prairies, and recorded the changing landscape from timbered eastern Missouri to western grasslands. The return to St. Louis ended hopes for a Northwest Passage, though the expedition had reached the Pacific after crossing the Rocky Mountains, met nearly 50 Indian nations, compiled extensive scientific records including 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.