The Lewis and Clark Expedition began in 1804, when President Thomas Jefferson tasked Meriwether Lewis with exploring the lands west of the Mississippi River that comprised the Louisiana Purchase. Lewis chose William Clark as his co-leader for the mission. The excursion lasted over two years. Along the way they confronted harsh weather, unforgiving terrain, treacherous waters, injuries, starvation, disease and both friendly and hostile Native Americans. Nevertheless, the approximately 8,000-mile journey was deemed a huge success and provided new geographic, ecological and cultural information about previously uncharted areas of North America.

Who Were Lewis and Clark?

Meriwether Lewis was born in Virginia in 1774 but spent his early childhood in Georgia. He returned to Virginia as a teenager to receive his education and graduated from college in 1793. He then joined the Virginia state militia—where he helped to put down the Whiskey Rebellion—and later became a captain in the U.S. Army. At age 27 he became personal secretary to President Thomas Jefferson.

William Clark was also born in Virginia in 1770 but moved with his family to Kentucky at age 15. At age 19, he joined the state militia and then the regular Army, where he served with Lewis and was eventually commissioned by President George Washington as a lieutenant of infantry.

In 1796, Clark returned home to manage his family’s estate. Seven years later, Lewis chose him to embark on the epic excursion that would help shape America’s history.

Louisiana Purchase

During the French and Indian War, France surrendered a large part of Louisiana to Spain and almost all of its remaining lands to Great Britain.

Initially, Spain’s acquisition didn’t have a major impact since it still allowed the United States to travel the Mississippi River and use New Orleans as a trade port. Then Napoleon Bonaparte took power in France in 1799 and wanted to regain France’s former territory in the United States.

In 1802, King Charles IV of Spain returned the Louisiana Territory to France and revoked America’s port access. In 1803, under the threat of war, President Jefferson and James Monroe successfully negotiated a deal with France to purchase the Louisiana Territory—which included about 827,000 square miles—for $15 million.

Even before negotiations with France were finished, Jefferson asked Congress to finance an expedition to survey the lands of the so-called Louisiana Purchase and appointed Lewis as expedition commander.

Preparations for the Lewis and Clark Expedition

preparations immediately. He studied medicine, botany, astronomy and zoology and scrutinized existing maps and journals of the region. He also asked his friend Clark to co-command the expedition.

Even though Clark was once Lewis’ superior, Lewis was technically in charge of the trip. But for all intents and purposes, the two shared equal responsibility.

On July 5, 1803, Lewis visited the arsenal at Harper’s Ferry to obtain munitions. He then rode a custom-made, 55-foot keelboat—also called “the boat” or “the barge”—down the Ohio River and joined Clark in Clarksville, Indiana. From there, Clark took the boat up the Mississippi River while Lewis continued along on horseback to collect additional supplies.

Some of the supplies collected were:

  • surveying instruments including compasses, quadrants, telescope, sextants and a chronometer
  • camping supplies including oilcloth, steel flints, tools, utensils, corn mill, mosquito netting, fishing equipment, soap and salt
  • clothing
  • weapons and ammunition
  • medicines and medical supplies
  • books on botany, geography and astronomy
  • maps

Lewis also collected gifts to present to Native Americans along the journey such as:

  • beads
  • face paint
  • knives
  • tobacco
  • ivory combs
  • bright colored cloth
  • ribbons
  • sewing notions
  • mirrors

Corps of Discovery

Lewis entrusted Clark to recruit men for their “Corps of Volunteers for Northwest Discovery,” or simply the Corps of Discovery. Throughout the winter of 1803-1804, Clark recruited and trained men at Camp DuBois north of St. Louis, Missouri. He chose unmarried, healthy men who were good hunters and knew survival skills.

The expedition party included 45 souls including Lewis, Clark, 27 unmarried soldiers, a French-Indian interpreter, a contracted boat crew and an enslaved person owned by Clark named York.

On May 14, 1804, Clark and the Corps joined Lewis in St. Charles, Missouri and headed upstream on the Missouri River in the keelboat and two smaller boats at a rate of about 15 miles per day. Heat, swarms of insects and strong river currents made the trip arduous at best.

To maintain discipline, Lewis and Clark ruled the Corps with an iron hand and doled out harsh punishments such as bareback lashing and hard labor for those who got out of line.

On August 20 of that year, 22-year-old Corps member Sergeant Charles Floyd died of an abdominal infection, possibly appendicitis. He was the only member of the Corps to die on their journey.

Native American Encounters

Most of the land Lewis and Clark surveyed was already occupied by Native Americans. In fact, the Corps encountered around 50 different Native American tribes including the Shoshone, the Mandan, the Minitari, the Blackfeet, the Chinook and the Sioux.

Lewis and Clark developed a first contact protocol for meeting new tribes. They bartered goods and presented the tribe’s leader with a Jefferson Indian Peace Medal, a coin engraved with the image of Thomas Jefferson on one side and an image of two hands clasped beneath a tomahawk and a peace pipe with the inscription, “Peace and Friendship” on the other.

They also told the Indians that America owned their land and offered military protection in exchange for peace.

Some Indians had met “white men” before and were friendly and open to trade. Others were wary of Lewis and Clark and their intentions and were openly hostile, though seldom violent.

In August, Lewis and Clark held peaceful Indian councils with the Odo, near present-day Council Bluffs, Iowa, and the Yankton Sioux at present-day Yankton, South Dakota.

In late September, however, they encountered the Teton Sioux, who weren’t as accommodating and tried to stop the Corps’ boats and demanded a toll payment. But they were no match for the military weapons of the Corps, and soon moved on.

Fort Mandan

In early November, the Corps came across villages of friendly Mandan and Minitari Indians near present-day Washburn, North Dakota, and decided to set up camp downriver for the winter along the banks of the Missouri River.

Within about four weeks they’d built a triangular-shaped fort called Fort Mandan, which was surrounded by 16-foot pickets and contained quarters and storage rooms.

The Corps spent the next five months at Fort Mandan hunting, forging and making canoes, ropes, leather clothing and moccasins while Clark prepared new maps. According to Clark’s journal, the men were in good health overall, other than those suffering from sexually transmitted infections.


While at Fort Mandan, Lewis and Clark met French-Canadian trapper Toussaint Charbonneau and hired him as an interpreter. They allowed his pregnant Shoshone wife, Sacagawea, to join him on the expedition.

Sacagawea had been kidnapped by Hidatsa Indians at age 12 and then sold to Charbonneau. Lewis and Clark hoped she could help them communicate with any Shoshone they’d encounter on their journey.

On February 11, 1805, Sacagawea gave birth to a son and named him Jean Baptiste. She became an invaluable and respected asset for Lewis and Clark.

The Continental Divide

On April 7, 1805, Lewis and Clark sent some of their crew and their keelboat loaded with zoological and botanical samplings, maps, reports and letters back to St. Louis while they and the rest of the Corps headed for the Pacific Ocean.

They crossed through Montana and made their way to the Continental Divide via Lemhi Pass where, with Sacagawea’s help, they purchased horses from the Shoshone. While there, Sacagawea reunited with her brother Cameahwait, who hadn’t seen her since she was kidnapped.

The group next headed out of Lemhi Pass and crossed the Bitterroot Mountain Range using the harrowing Lolo Trail and the help of many horses and a handful of Shoshone guides.

This leg of the journey proved to be the most difficult. Many of the party suffered from frostbite, hunger, dehydration, bad weather, freezing temperatures and exhaustion. Still, despite the merciless terrain and conditions, not a single soul was lost.

After 11 days on the Lolo Trail, the Corps stumbled upon a tribe of friendly Nez Perce Indians along Idaho’s Clearwater River. The Indians took in the weary travelers, fed them and helped them regain their health.

As the Corps recovered, they built dugout canoes, then left their horses with the Nez Perce and braved the Clearwater River rapids to Snake River and then to the Columbia River. They reportedly ate dog meat along the way instead of wild game.

Fort Clatsop

A bedraggled and harried Corps finally reached the stormy Pacific Ocean in November of 1805. They’d completed their mission and had to find a place to live for the winter before heading home.

They decided to make camp near present-day Astoria, Oregon, and started building Fort Clatsop on December 10 and moved in by Christmas.

It was not an easy winter at Fort Clatsop. Everyone struggled to keep themselves and their supplies dry and fought an ongoing battle with tormenting fleas and other insects. Almost everyone was weak and sick with stomach problems (likely caused by bacterial infections), hunger or influenza-like symptoms.

Lewis and Clark Journey Home

On March 23, 1806, the Corps left Fort Clatsop for home. They retrieved their horses from the Nez Perce and waited until June for the snow to melt to cross the mountains into the Missouri River Basin.

After again traversing the rugged Bitterroot Mountain Range, Lewis and Clark split up at Lolo Pass.

Lewis’ group took a shortcut north to the Great Falls of the Missouri River and explored Marias River—a tributary of the Missouri in present-day Montana—while Clark’s group, including Sacagawea and her family, went south along the Yellowstone River. The two groups planned to rendezvous where the Yellowstone and Missouri met in North Dakota.

HISTORY Vault: Lewis and Clark: Explore New Frontier

Discover the adventures of Meriwether Lewis and William Clark as they traversed the vast, unknown continent of North America.

Pompey’s Pillar

On July 25, 1806, Clark carved his name and the date on a large rock formation near the Yellowstone River he named Pompey’s Pillar, after Sacagawea’s son whose nickname was “Pompey.” The site is now a national monument managed by the U.S. Department of the Interior.

Two days later, at Marias River near present-day Cut Bank, Montana, Lewis and his group encountered eight Blackfeet warriors and were forced to kill two of them when they tried to steal weapons and horses. The location of the clash became known as Two Medicine Fight Site.

It was the only violent episode of the expedition, although soon after the Blackfeet fight, Lewis was accidentally shot in his buttocks during a hunting trip; the injury was painful and inconvenient but not fatal.

On August 12, 1806, Lewis and Clark and their crews reunited and dropped off Sacagawea and her family at the Mandan villages. They then headed down the Missouri River—with the currents moving in their favor this time—and arrived in St. Louis on September 23, where they were received with a hero’s welcome.

Legacy of the Expedition 

Lewis and Clark returned to Washington, D.C., in the fall of 1806 and shared their experiences with President Jefferson.

While they had failed to identify a coveted Northwest Passage water route across the continent, they had completed their mission of surveying the Louisiana Territory from the Mississippi River to the Pacific Ocean, and did so against tremendous odds with just one death and little violence.

The Corps had traveled more than 8,000 miles, produced invaluable maps and geographical information, identified at least 120 animal specimens and 200 botanical samples and initiated peaceful relations with dozens of Native American tribes.

Both Lewis and Clark received double pay and 1,600 acres of land for their efforts. Lewis was made Governor of the Louisiana Territory and Clark was appointed Brigadier General of Militia for Louisiana Territory and a federal Indian Agent.

Clark remained well-respected and lived a successful life. Lewis, however, was not an effective governor and drank too much. He never married or had children and died in 1809 of two gunshot wounds, possibly self-inflicted. A few years later, Sacagawea died, and Clark became her children’s guardian.

Despite Lewis’ tragic end, his expedition with Clark remains one of America’s most famous. The duo and their crew—with the aid of Sacagawea and other Native Americans—helped strengthen America’s claim to the West and inspired countless other explorers and western pioneers.


Building Fort Clatsop. Discovering Lewis & Clark.
Corps of Discovery. National Park Service: Gateway Arch.
Expedition Timeline. Thomas Jefferson Foundation: The Jefferson Monticello.
Flagship: Keelboat, Barge or Boat? Discovering Lewis & Clark.
Fort Clatsop Illnesses. Discovering Lewis & Clark.
Fort Mandan Winter. Discovering Lewis & Clark.
Indian Peace Medals. Thomas Jefferson Foundation: The Jefferson Monticello.
Lemhi Valley to Fort Clatsop. Discovering Lewis & Clark.
Lolo Trail. National Park Service: Lewis and Clark Expedition.
Louisiana Purchase. Thomas Jefferson Foundation: The Jefferson Monticello.
The Journey. National Park Service: Lewis and Clark Expedition.
The Native Americans. PBS.
To Equip an Expedition. PBS.
Two Medicine Fight Site. National Park Service: Lewis and Clark Expedition.
Washington City to Fort Mandan. Discovering Lewis & Clark.