Lewis and Clark crossed the Bitterroot Mountain Range, a northern segment of the Rocky Mountains. Though the peaks of the Bitterroots average 9,000 to more than 11,000 feet, they found a westward route over the mountains through Lolo Pass, which is at an elevation of 5,236 feet.
One of the primary goals of Lewis and Clark's expedition was to search for the Northwest Passage, a hypothetical water route from the Atlantic Ocean to the Pacific Ocean. Other goals included making diplomatic contact with Native Americans, extending the fur trade into new territories, and exploring the Missouri River, the Pacific Northwest and the newly bought Louisiana Purchase. They set out up the Missouri River in May 1804 with 33 other men. In North Dakota, they built Fort Mandan within which to wait out the winter. In April 1805, they continued along the Missouri until they reached the Rocky Mountains, where they had to continue on horseback. On the other side of the Continental Divide, they continued by canoe down the Clearwater and Snake Rivers until they reached the Columbia River, which took them the rest of the way to the Pacific.
Lewis and Clark and the men of their expedition, called the Corps of Discovery, arrived back in St. Louis in September 1806 after having traveled almost 8,000 miles. They were received as heroes by President Thomas Jefferson, Congress and the American public.