Mapping the Corps of Discovery

Up the Missouri and Over the Mountains

1In 1803 the United States agreed to buy the Louisiana Territory from France for about $15 million. France's leader, Napoleon Bonaparte, needed money for war in Europe, and a revolution in Haiti had ended his plans for an empire in the Americas. President Thomas Jefferson had first hoped only to buy the port of New Orleans, which farmers west of the Appalachian Mountains used to ship crops down the Mississippi River. Jefferson worried that the Constitution did not clearly give the government power to buy land, but he decided the chance was too important to miss. The Senate approved the treaty, and the size of the country roughly doubled.

2Few Americans knew what the new land held. Jefferson asked Meriwether Lewis to lead an expedition, and Lewis chose William Clark to share command. Their orders were to follow the Missouri River toward its source, look for a water route to the Pacific Ocean, record plants, animals and land, and build trade ties with Native nations. The group, called the Corps of Discovery, included soldiers, boatmen, hunters and York, an enslaved man owned by Clark.

3The Corps left the St. Louis area in May 1804 and pushed its boats up the Missouri against the current. That fall it reached the villages of the Mandan and Hidatsa peoples and built Fort Mandan for the winter. There the leaders hired a French Canadian trader, Toussaint Charbonneau, and his wife Sacagawea, a Lemhi Shoshone woman who had been captured as a girl. In April 1805 the Corps headed west again. At the Great Falls of the Missouri, the men spent about a month carrying their canoes and supplies overland around the waterfalls.

4In August 1805, near the Continental Divide, the Corps met a band of Shoshone. Their leader, Cameahwait, turned out to be Sacagawea's brother. The Shoshone traded the horses the Corps needed to cross the Rocky Mountains. The crossing of the Bitterroot Mountains that fall was cold, and food ran low. When the hungry men came down from the mountains, the Nez Perce fed them and showed them how to make canoes by burning out logs. The Corps then traveled down rivers that flowed west and reached the Pacific coast in November 1805.

5The Corps returned to St. Louis in September 1806. Lewis and Clark had not found an all-water route to the Pacific, but their maps and journals described a huge land and the many nations living on it. The United States later pointed to the expedition when it claimed the Oregon Country. In the decades that followed, fur traders and then settlers moved west, and by the 1840s many Americans believed in "manifest destiny," the idea that the United States was meant to spread across the continent. The Native nations who had traded with and helped the Corps saw that land as their own homes. Over time many of them lost much of their land through treaties, wars and forced moves.