The United States acquired the Missouri River watershed through the Louisiana Purchase of 1803, and President Thomas Jefferson sent Meriwether Lewis and William Clark with a company of men to explore up the Missouri in the hopes of finding a navigable water route to the Pacific, with a low portage connecting one watershed with the other. The Expedition departed from Saint Louis, Missouri in the spring of 1804, ascended the Missouri River that summer, then wintered over with the Hidatsa Indians in North Dakota, where they met Toussaint Charbonneau and his Shoshone wife Sacagawea. Lewis and Clark hired Charbonneau to join the expedition, in part because Sacagawea's people were native to the Missouri headwaters. The Lewis and Clark Expedition arrived at the Missouri Headwaters on 27 July 1805.