Lewis and Clark explored the Louisiana Purchase. President Thomas Jefferson commissioned them to follow the Missouri River to its headwaters and then find a route to the Pacific. Guided by the maps of the time, which presented conflicting views of the territory, the expedition set out in 1804. The group, which consisted of Lewis and Clark, 26 army regulars, two rivermen, Clark's slave York, and a French interpreter, spent the first winter in the Mandan villages at the mouth of the Missouri. There they acquired the services of an interpreter, Charbonneau. With him came his Shoshone wife, Sacagawea.
On June 13, 1805, they saw the spray from the great falls of the Missouri, which presented a huge barrier that would take a month of hard labor to portage around. In spite of the mosquitoes and grizzly bears, the group finally succeeded in moving their gear around the falls. Making their way up river, along the border of Bird Creek Ranch and through the Gates of the Mountains, they reached the headwaters of the Missouri and shortly after found Sacagawea's people, who supplied the group with horses for the push across the mountains.
After spending the winter of 1805 at Fort Clatsop, they headed home in the spring of 1806. They went back up the Columbia River, for part of the trip home, dividing their command in Montana, and reuniting at Great Falls. The group successfully returned to St. Louis in September of 1806.
The expedition revealed to the world the wonders of western territory and underlined the economic value of the holding for the young nation. However, the expedition leaders became more than explorers. Lewis and Clark came to symbolize America's rootless westering spirit.