corpsofdiscovery.org

The Lewis and Clark Expedition (1804–1806) was the first U.S. overland journey to the Pacific Coast and back, led by Meriwether Lewis and William Clark under the name Corps of Discovery. It matters today because it produced some of the earliest written and mapped records of the American West, and because the route it followed is now marked by interpretive sites, museums, and trail organizations you can visit. This explainer covers who was involved, where they went, what went wrong, and how to follow the trail yourself.

Who Lewis and Clark Were, and Why the Corps of Discovery Existed

Meriwether Lewis was an army captain and private secretary to President Thomas Jefferson. William Clark was a soldier and mapmaker who shared command of the journey. Jefferson commissioned the expedition to find a practical water route across the continent, study the land, and document its peoples, plants, and animals.

The group they led, the Corps of Discovery, was a military-style party of roughly three dozen people at its core, supplemented by interpreters, boatmen, and others who joined for parts of the trip.

Key Figures Beyond the Two Captains

The expedition is often remembered through a handful of people whose contributions shaped its survival and its story.

The Route: St. Louis to the Pacific and Back

The journey ran in two broad halves.

Outbound (1804–1805)

• Departed from the St. Louis area in May 1804, moving up the Missouri River.
• Wintered at Fort Mandan in present-day North Dakota, where Sacagawea and her husband Toussaint Charbonneau joined.
• Crossed the Continental Divide, obtained horses from the Shoshone, and descended the Clearwater, Snake, and Columbia rivers.
• Reached the Pacific Coast in November 1805 and built Fort Clatsop for the winter.

Return (1806)

• Split into separate parties to explore different routes, then reunited.
• Returned to St. Louis in September 1806.

Major Challenges: The Great Falls Portage

One of the hardest stretches came in present-day Montana, where the party hit a series of waterfalls on the Missouri River. Rather than float through, they had to haul canoes and supplies overland around the falls — a slow, exhausting portage across rough ground in punishing heat.

That episode is why the Great Falls area remains a center of Lewis and Clark interpretation today. The Portage Route Chapter of the Lewis and Clark Trail Alliance, founded in 1983 and headquartered in Great Falls, Montana, is one of the oldest chapters of the national alliance and focuses on educating the public about the expedition and preserving the trail in that region.

How to Explore Trail Sites and Interpretive Centers Today

If you want to follow the story on the ground, the trail is organized through the Lewis and Clark Trail Alliance and its local chapters.

• Start with a chapter or the national alliance. The Portage Route Chapter's site includes a blog, partner links (including the Portage Route Chapter and the Lewis and Clark Honor Guard), and a Contact page for membership questions.
• Check for events. The alliance's 2026 Annual Meeting is scheduled for June 21–24 in Great Falls, hosted by the Portage Route Chapter — a concrete reason to plan a visit around that window.
• Use interpretive centers as anchors. The alliance's home office is headquartered in Great Falls at the Lewis and Clark Interpretive Center, which also houses the William P. Sherman Library and Archives.
• Look for field trips and tours. The chapter offers field trips and tours to sites along the trail and works to identify, develop, and maintain interpretive sites and signage.

Why It Still Matters

The expedition's journals and maps are among the founding documents of the American West, and the trail network built around them keeps that record accessible. Organizations like the Portage Route Chapter — a 501(c)(3) nonprofit and Montana nonprofit corporation — exist specifically to keep the story accurate and the sites preserved, which is what makes the trail something you can still visit rather than just read about.

Sacagawea was a Shoshone woman who, as a teenager, joined the Lewis and Clark Expedition (the Corps of Discovery) in 1805 and served as an interpreter and cultural intermediary during its push to the Pacific. She is most closely associated with the expedition's passage over the Rocky Mountains, where her presence and connections helped the party obtain horses from the Shoshone. Her significance today rests less on any single dramatic act than on the range of practical roles she filled—translator, guide, diplomat, and symbol—and on how those roles have been remembered, debated, and sometimes exaggerated.

Who Sacagawea Was

Sacagawea was born into the Lemhi Shoshone (also called the Agaidika or Salmon Eater band) in the region that is now Idaho and Montana. As a young girl she was captured by a Hidatsa raiding party and taken to villages along the upper Missouri River, where she was later purchased by or married to Toussaint Charbonneau, a French Canadian trader and interpreter who lived among the Hidatsa.

When the Corps of Discovery wintered at Fort Mandan (1804–1805), Meriwether Lewis and William Clark hired Charbonneau as an interpreter. Sacagawea, then about sixteen and pregnant, was brought along as part of the arrangement. She gave birth to her son, Jean Baptiste Charbonneau—nicknamed "Pomp"—in February 1805, before the expedition departed upriver that spring.

Her Practical Contributions

Sacagawea's value to the expedition was concrete and varied. The most commonly cited contributions include:

• Interpreting and facilitating communication. Because she spoke Shoshone and had learned Hidatsa, she could communicate with Hidatsa speakers, and Charbonneau could translate between Hidatsa and French. This chain of translation allowed the captains to negotiate with Shoshone bands.
• Obtaining horses. When the expedition reached the Shoshone in the summer of 1805, Sacagawea recognized the band's leader, Cameahwait, as her brother. This reunion helped the party secure the horses needed to cross the Bitterroot Range—a critical logistical turning point.
• Signaling peaceful intent. The presence of a woman and an infant with the party signaled to Native nations that this was not a war party. Clark later credited her presence with helping to defuse tense encounters.
• Knowledge of the landscape and food. She identified edible plants and roots along the route and recalled landmarks from her childhood homeland, which aided navigation in the Rockies.

Key Moments on the Journey

One frequently cited episode is the vote at Fort Clatsop on where to winter. Sacagawea and York, an enslaved man in the party, were included in that decision—an unusual inclusion for the era, and one often noted as a sign of her standing within the group.

Common Myths and Misconceptions

Popular memory has often inflated or distorted Sacagawea's role. A few corrections are worth keeping in mind:

• She was not the expedition's sole guide. The Corps relied on multiple Native guides and on its own members' skills. Sacagawea's knowledge was valuable but not the single thread that saved the journey.
• She did not "lead" Lewis and Clark across the continent. She was a teenager with limited knowledge of much of the route, especially the regions east of her homeland.
• Her later life is poorly documented. Accounts of her death vary; some place it in 1812 at Fort Manuel Lisa, while others claim she lived longer. The record is thin, and claims should be treated cautiously.
• Her name has many spellings. "Sacagawea," "Sacajawea," and "Sakakawea" are all used; the spelling often reflects regional or tribal preference rather than a single correct form.

Her Legacy and How She Is Remembered

Sacagawea is commemorated in statues, place names, coins, and interpretive sites across the American West, including along the Lewis and Clark National Historic Trail. The Portage Route Chapter of the Lewis and Clark Trail Alliance, based in Great Falls, Montana, is one of the organizations that works to preserve and interpret the trail in the region where the expedition portaged around the Great Falls of the Missouri. The chapter traces its roots to the mid-1800s, when travelers began recording their impressions of the "land of Lewis and Clark," and it continues to maintain interpretive sites and signage along the route.

For many Native communities, Sacagawea is remembered not only as an expedition member but as an ancestor and a symbol of Shoshone and Hidatsa heritage. Her story is a reminder that the expedition depended on Indigenous knowledge and cooperation—a fact that popular narratives have sometimes minimized.

Why She Still Matters

Sacagawea matters because she illustrates how exploration and diplomacy actually worked: through translation, kinship, and local knowledge, not just through the efforts of the two captains. She was a young woman in an unfamiliar and often dangerous situation who made herself useful in ways that shaped the expedition's outcome. Her life also raises enduring questions about whose stories get told, how they are told, and what is lost when they are simplified.

The Corps of Discovery was the official name of the party that carried out the Lewis and Clark Expedition (1804–1806), sent by President Thomas Jefferson to explore the newly acquired Louisiana Purchase and find a route to the Pacific. If you want to understand what the expedition actually was, who made it work, and why it still matters, the Corps is the right starting point — it is the expedition's organizational identity, not a separate event.

What the Corps of Discovery Was

The Corps of Discovery was a U.S. Army unit assembled for a specific mission: explore the Missouri River, seek a practical water route across the continent, document the land, peoples, plants, and animals encountered, and establish American presence in the West. Meriwether Lewis was commissioned to lead it, and he chose William Clark as co-commander. The party is often described as a "corps" because it was organized and disciplined along military lines, which mattered for survival, record-keeping, and diplomacy with Native nations.

Who Was in It

The Corps was small, but its roles were distinct. The best-known members:

• Meriwether Lewis — Jefferson's private secretary, tasked with scientific observation and overall command.
• William Clark — co-leader, mapmaker, and field commander; his journals and sketches are central to what we know about the route.
• Sacagawea — a Shoshone woman who joined the expedition as an interpreter and guide; her presence and knowledge were important in negotiating for horses and crossing the Rockies.
• York — an enslaved man held by Clark, who took part in the journey and whose role is increasingly recognized in interpretation of the expedition.
• Seaman — Lewis's Newfoundland dog, who traveled with the party and appears in expedition records.

Beyond these figures, the Corps included enlisted soldiers, boatmen, hunters, and interpreters. The Portage Route Chapter of the Lewis and Clark Trail Alliance, based in Great Falls, Montana, is one of the organizations that keeps this history public through programs, field trips, and interpretive sites along the trail.

Route, Timeline, and Main Accomplishments

The expedition ran from 1804 to 1806, traveling up the Missouri River, across the Rocky Mountains, and down to the Pacific coast before returning. Its accomplishments include:

• Mapping and describing a vast portion of the American West.
• Documenting Native American nations, languages, and trade networks.
• Collecting plant and animal specimens previously unknown to Euro-American science.
• Demonstrating that an all-water route across the continent did not exist as hoped, which reshaped American understanding of the West.

The "portage" in the Portage Route Chapter's name refers to the difficult overland carry around the Great Falls of the Missouri — a key logistical challenge the Corps had to solve.

Why the Corps Still Matters

The Corps of Discovery is more than a historical label. It is the framework through which the expedition's mission, membership, and legacy are understood. Modern groups such as the Portage Route Chapter and the national Lewis and Clark Trail Alliance preserve and interpret the trail, maintain signage and sites, and host gatherings — including the Alliance's 2026 Annual Meeting in Great Falls, June 21–24. If you are researching the expedition, planning a trail visit, or looking for a local chapter, the Corps is the thread that connects the original journey to today's stewardship.

For related background, see the companion explainers on Sacagawea's role and on the Lewis and Clark Expedition as a whole.

The Lewis and Clark Expedition was the United States' first official overland journey to the Pacific Coast, led by Meriwether Lewis and William Clark between 1804 and 1806. Its members, known as the Corps of Discovery, were tasked with exploring the newly acquired Louisiana Purchase, seeking a practical water route across the continent, and documenting the peoples, plants, animals, and geography they encountered. The expedition matters today because it produced some of the earliest systematic records of the American West and became a founding story of U.S. exploration.

What the Expedition Was

After the U.S. purchased the Louisiana Territory from France in 1803, President Thomas Jefferson commissioned an expedition to explore the region and beyond. Lewis, Jefferson's private secretary, was chosen to lead it, and he selected Clark as co-commander. The journey formally began in 1804 near St. Louis and ended in 1806 when the party returned east.

The group that traveled together is called the Corps of Discovery. It was a military-style unit with civilians attached, and its members kept journals that remain primary sources for historians.

Who Led It and Who Was in It

• Meriwether Lewis — co-leader; responsible for scientific observation and record-keeping.
• William Clark — co-leader; handled mapmaking, navigation, and much of the day-to-day command.
• Sacagawea — a Shoshone woman who joined the expedition as an interpreter and guide; her presence and knowledge aided diplomacy and travel.
• York — an enslaved man belonging to Clark, who took part in the journey and is noted in the journals for his role in the party.
• Seaman — Lewis's Newfoundland dog, who accompanied the expedition.

The Corps also included enlisted soldiers, boatmen, and hunters whose labor kept the journey moving.

What the Expedition Set Out to Do

Jefferson's instructions gave the expedition several overlapping goals:

1. Explore the Louisiana Purchase and the lands beyond it.
2. Find a water route across the continent to the Pacific, ideally a continuous river passage.
3. Document the natural world — plants, animals, and geography.
4. Record the peoples encountered, including their cultures, languages, and trade.
5. Establish U.S. presence and diplomatic contact with Native nations.

The expedition did not find a single continuous water route, but it mapped and described a vast region that was largely unknown to the U.S. government at the time.

The Great Falls Portage

One of the most demanding sections of the route was the portage around the Great Falls of the Missouri River, in what is now Montana. The party had to carry their canoes and supplies overland past a series of waterfalls, a labor-intensive detour that took weeks. This area is central to the story of the expedition in the Great Falls region and is the focus of the Portage Route Chapter of the Lewis and Clark Trail Alliance, a local organization based in Great Falls that works to preserve and interpret the trail.

Why It Still Matters

The expedition's journals and maps became foundational records of the American West. They documented species, landscapes, and Indigenous nations that were new to U.S. science and government at the time. The journey also shaped how the United States understood its western territory and its ambitions.

Today, the expedition is remembered through trail alliances, interpretive centers, and local chapters — including the Portage Route Chapter — that maintain markers, host programs, and educate the public about the Corps of Discovery's route and legacy.

The Portage Route was the roughly 18-mile overland carry the Corps of Discovery had to make around the five falls of the Missouri River near present-day Great Falls, Montana. The expedition could not move its canoes and heavy supplies through the falls by water, so the men hauled everything across the prairie instead. The detour cost them far more time and labor than they expected, and it became one of the best-documented ordeals of the journey. If you want to follow the story or visit the sites, the route and its markers are still traceable today, and the Portage Route Chapter of the Lewis and Clark Trail Alliance in Great Falls works to preserve and interpret them.

Why the expedition had to portage at all

The Missouri River above and below the falls is navigable in stretches, but the five falls themselves are a series of cascades and drops that no loaded canoe could safely run or line through. Lewis and Clark had been told by Native informants and earlier traders that a short carry would get them past the obstruction. The reality was a set of separate falls spread across miles of broken country.

The Corps therefore had to:

• Unload the canoes and cache or carry the supplies.
• Drag the canoes overland, sometimes on improvised carriages made from cottonwood wheels and axles.
• Move the load in relays, which meant walking the route multiple times.
• Contend with prickly pear, rough ground, heat, and mosquitoes.

The work stretched from roughly mid-June into July 1805 and consumed weeks rather than the few days the party had hoped for. Rain, heat, and injuries to feet and legs slowed the carry further. The portage is often described as one of the hardest physical episodes of the entire expedition.

What the route covered

The portage ran from the area of the lower falls to a point above the upper falls, bypassing all five. The falls, in the order the expedition encountered them, are commonly named:

The route crossed what is now the city of Great Falls and surrounding land. Because the falls have been altered by dams and development, the modern landscape does not match what the Corps saw, but interpretive markers and sites along the way still tell the story.

Why it mattered

The portage mattered for three reasons:

1. It tested the expedition's endurance. The carry pushed the men and their equipment to the limit and shaped how they planned the rest of the journey.
2. It confirmed the geography. The falls told Lewis and Clark they were on the right river system and approaching the mountains, which mattered for the larger goal of finding a water route to the Pacific.
3. It left a detailed record. The journals describe the falls, the portage, and the surrounding country in enough detail that historians and visitors can reconstruct the experience.

Sacagawea, York, and the rest of the party were part of this stretch of the journey, and the portage is one of the episodes where the full company's labor is visible in the record.

Visiting the route and the falls today

If you want to see the ground the Corps crossed, Great Falls, Montana, is the base. The area offers:

• Interpretive sites and signage along the historic route, maintained in part through the work of the Portage Route Chapter.
• The falls themselves, though dams have changed their appearance from 1805.
• The Lewis and Clark Interpretive Center in Great Falls, which also houses the Alliance's home office and the William P. Sherman Library and Archives.

The Portage Route Chapter, founded in 1983, is one of the oldest chapters of the Lewis and Clark Trail Alliance. It is headquartered in Great Falls, maintains a membership of about 50, and describes its objectives as educating the public about the expedition and preserving the trail in the area. It also offers field trips and tours to sites along the trail and works to identify, develop, and maintain interpretive sites and signage.

Events and membership

The chapter hosts programs and projects with partners, and it holds its annual meeting in September, when board members are elected from the membership. The national Lewis and Clark Trail Alliance is hosting its 2026 Annual Meeting in Great Falls from June 21–24, and the Portage Route Chapter is the host chapter.

To learn about membership in the chapter or the national Alliance, the chapter directs visitors to its Contact Us page. The chapter is registered with the IRS as a 501(c)(3) nonprofit and is also a Montana nonprofit corporation.

Quick answers

What was the Portage Route? An approximately 18-mile overland carry around the five falls of the Missouri River near present-day Great Falls, Montana.

Why did the Corps of Discovery portage? The falls were impassable by loaded canoe, so the party hauled canoes and supplies across land.

How long did it take? Weeks, from roughly mid-June into July 1805, far longer than expected.

Where can I see it today? In and around Great Falls, Montana, through interpretive sites, markers, the falls, and the Lewis and Clark Interpretive Center.

Who preserves it? The Portage Route Chapter of the Lewis and Clark Trail Alliance, based in Great Falls.