Lewis and Clark Expedition: What It Was, Who Led It, and Why It Matters

Updated

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.