President Thomas Jefferson asks Congress for $2,500 to fund a scientific expedition of the west and recommends his personal secretary, Meriwether Lewis, as its leader. Both requests are granted. In a country where most of the population lives within 50 miles of the Atlantic Ocean, knowledge of the area west of the Mississippi River is limited to information learned from French fur trappers and European explorers. For the first time, an official expedition by the United States to map the uncharted land is set.
Jefferson buys the Louisiana Territory from France for $15 million. More than 800,000 square miles (2.1 million sq km) of land stretching from the Mississippi River to the Rocky Mountains now belongs to the United States. The size of the country is doubled for just three cents an acre, the port of New Orleans is secured after years of instability, and Lewis' expedition must establish diplomatic ties with the Native Americans who now occupy half the nation.
Lewis writes a letter to William Clark asking him to join the newly formed army division called Corps of Discovery.
Jefferson finalizes his instructions for the Expedition. Lewis is to search for a continuous water route across the continent, establish trade with the Native American people, and study the plants, animals, and landscape of the west. The discovery of a way to cross the entire continent by boat was extremely important for quicker trade routes and cheaper commerce, but a waterway connecting the Pacific and Atlantic Oceans would not exist until the opening of the Panama Canal in 1914.
Clark accepts Lewis' offer and joins the Corps of Discovery as a Second Lieutenant. He is lower in rank than Lewis in title only. Besides holding co-captaincy with Lewis, he is in charge of drawing maps, managing supplies, and leading hunting parties for bison and elk.
Lewis and Clark arrive at Camp Dubois near present-day Hartford, Illinois, after months of gathering supplies and recruits. They will spend the winter there and leave when spring arrives.
The Corps of Discovery leaves Camp Dubois. Nearly four-dozen men consisting of soldiers, carpenters, one slave, and a dog travel in a 55-foot long keelboat and two smaller boats called pirogues. They sail, row, push with poles, and pull the boats with ropes to move up the strong current of the Missouri River. Progress is slow and 15 miles is a good day's journey.
Lewis and Clark hold their first official council with Native Americans. They meet a small delegation of Oto and Missouri Indians to hand out peace medals and gifts. Trade talks and peace negotiations are also held. Lewis wants the Oto and Missouri to stop their raids on the neighboring Omaha tribe. The Oto are more interested in a establishing a reliable, open-trade system with the Untied States. The procedures set the basis for the following councils they will hold with the almost 50 different tribes they meet on the expedition.
Sergeant Charles Floyd dies from a burst appendix near what is now Sioux City, Iowa. He is the only member of the Corps to die during the journey and the first United States soldier to die west of the Mississippi.
The captains hire French-Canadian fur trader Toussaint Charbonneau as an interpreter in modern day North Dakota. His Shoshone wife, Sacagawea, becomes the only woman to join the expedition. They believe she will be helpful when they try to buy horses from her people living at the headwaters of the Missouri.
The second winter headquarters of the expedition is completed. They name it Fort Mandan after the local Indian tribe that hosts them until spring.
The expedition of 31 men, one woman, a dog, and Sacagawea's newborn son starts up the Missouri River into uncharted territory.
Lewis and another man kill a grizzly bear in what is now Montana. The animal has never before been described scientifically. It is one of 178 plants and 122 animals discovered on the expedition and recorded for the first time.
The expedition stops at a fork in the river. The men believe the northern fork is the Missouri; Lewis and Clark think it's the southern fork. They scout for several days and still cannot come to an agreement, but the men promise to follow their two captains anywhere they lead. They head south with only the knowledge that if they find a waterfall, they are on the right path.
Lewis scouts ahead and discovers the Great Falls of the Missouri, proving he and Clark had been right. The toughest test of their command on the journey is over.
The Corps of Discovery become the first men to cross the Continental Divide. They leave the newly purchased territory of the United States and enter the disputed Oregon Country. Russia, Great Britain, Spain, and France all claim a hold on the land. The United States would soon join them due to the efforts of Lewis and Clark.
William Clark sees the mouth of the Colombia River and mistakes it for the Pacific Ocean. They are still 20 miles from the sea. High winds and storms prevent them from progressing for almost three weeks.
The expedition must decide where to spend the winter. Lewis and Clark put it to a vote. Clark's slave, York, is given a vote. This is almost 60 years before slaves in the United States would be freed or allowed suffrage. Sacagawea also votes, more than a century before either women or Indians are granted full rights as citizens. They decide to cross the Columbia River into modern-day Astoria, Oregon, to build their winter home.
Fort Clatsop is completed and named after the local Indian tribe. They will stay there, over 4,000 miles from home, for the next three and a half months. Most of their time is spent trading for food with local Indian tribes and preparing for the long trip back.
Fort Clatsop is given to the Clatsop Indians and the Corps of Discovery sets off for home.
The expedition crosses the Bitterroot Mountains and splits into two groups to explore more of the Louisiana Territory. Clark will head down the Yellowstone River and Lewis will explore the northernmost reaches of the Marias River.
Clark's group comes to a sandstone outcropping east of present-day Billings, Montana. He names it after Sacagawea's son and carves his own name and the date into the face of the rock. It is the only physical evidence of the expedition that survives today.
Blackfeet Indians try to steal Lewis' and his men's rifles. A fight breaks out and two of the Indians are killed. This is the only hostile encounter with an Indian tribe on the entire expedition. The expedition's mission of diplomacy with the Native Americans in the West is successful. However, tribal leaders have doubts as to whether leaders in Washington will keep the promises of peace Lewis and Clark have made.
The expedition is reunited downstream from the mouth of the Yellowstone River. They head toward the Missouri and home.
The Corps of Discovery members reach St. Louis and are greeted as heroes by cheering crowds. Over two years and 8,000 miles (12,900 km) since the beginning of their journey, they are home.