Why Was the Lewis and Clark Expedition Important?

Important Lewis and Clark Expedition

In 1804 one of the most well-known expeditions in the history of the United States began. Just what was the purpose of the Lewis and Clark expedition and why was it important?

Following the important 1803 Louisiana Purchase, President Thomas Jefferson prioritized the exploration of the new territory and entrusted his personal secretary Meriwether Lewis for the task.

Lewis recruited former army captain William Clark to be co-leader of the newly formed “Corps of Discovery” tasked with exploring the territory.

Jefferson had numerous motives for the Lewis and Clark expedition other than simple exploration. His enlightened Jeffersonian beliefs and ideals encapsulated a thirst for knowledge of the unknown and “undiscovered.”

For two years, four months, and ten days the Lewis and Clark expedition traversed the west. Over forty members made the trip covering nearly 8,000 miles and traveling through unfamiliar lands.

The group heavily relied upon the generosity of the powerful Native American nations they encountered and were lucky to have encountered an essential Native American guide in Sacajawea.

What the group encountered, documented, and brought back with them would forever change the course of American history.

The Purpose of the Lewis and Clark Expedition

The purpose of the Lewis and Clark expedition was twofold: to stake a claim to the Pacific northwest territory and establish trade routes through the region, particularly for the fur trade, as well as to promote the discoveries and advancement of science per enlightenment principles of the time period.

Jefferson had long been interested in the Louisiana territory. He was fascinated by British accounts from James Cook and Alexander MacKenzie of exploring the western edges of the continent, albeit through Canadian routes.

For nearly ten years prior to the trip Jefferson outlined goals for a future expedition. When the opportunity arose he was prepared, sensing an opportunity for the United States.1

Ever the diplomat, Jefferson secured letters of safe passage from Britain and France for the expedition to ensure no troubles would arise from their exploration into disputed territories.2

Lewis and Clark Native Americans
Depiction of Lewis and Clark with Native Americans via LOC

Staking a claim to the Pacific Northwest was paramount among Jefferson’s goals. He knew of British intentions to secure territorial claims and rights to the region, a scenario that could prove troublesome to the United States in the future.

Jefferson foresaw that the United States would need a port on the Pacific Ocean to facilitate trade in East Asia. If the British cut off access, and the Spanish access to the south, the United States would miss out.

The purpose of the expedition was to also help establish trade routes through the region and compete with Britain in the lucrative fur trade. Jefferson held out hope that Lewis and Clark would discover an all-water route through the interior to the Pacific ocean, though no such route ever emerged.

Lastly, Jefferson assured his foreign counterparts that the true purpose of the Lewis and Clark expedition was for the promotion of discoveries and advancement of science.2

A man of enlightened principles, knowledge reigned supreme and the discovery of plants, animals, and people heretofore unknown to western civilization piqued his interest like no other.

Why Was the Lewis and Clark Expedition Important?

The Lewis and Clark expedition was important for a variety of reasons but primarily as it discovered hundreds of new plants and animals, mapped a route to the Pacific Ocean, spurred Manifest Destiny, and opened diplomatic relations with the plains Native Americans.

Over the entire timeline of the Lewis and Clark Expedition, the team set a grueling pace that covered 7,689 miles in total.1

The corps encountered dozens of Native American nations, survived two winters, suffered through extreme heat, and a near endless number of illnesses.

Miraculously only one person did not survive the journey, perishing from an inoperable case of appendicitis. All considered, it was a mind-boggling feat for the time period.1

Why Lewis and Clark Expedition Important

Discovered New Plants and Animals

One of the most important results of the Lewis and Clark expedition was their “discovery” of hundreds of new plants and animals. These plants and animals weren’t truly discovered, it was merely the first time western explorers documented and introduced them to western civilization.

Native Americans, of course, had lived among these animals and knew of the properties of the plants in the Louisiana territory for centuries before Lewis and Clark documented them for western eyes.

In all, the Corps of Discovery collected 122 species of animals and 178 plant species never before described by western science.3

Some animals are well known amongst Americans today such as the grizzly bear, bighorn sheep, and prairie dog. Lewis became so fascinated by the prairie dog that he even captured and sent a live one to President Jefferson.

animal drawing Lewis Meriwether
Bird drawing from Lewis Meriwether’s journal via NPS

Their encounters with grizzly bears were much more harrowing. Lewis and Clark downplayed Native American warnings to avoid the bears but quickly learned just how dangerous they could be. From Lewis’ journal:

“it was a most tremendious looking anamal, and extreemly hard to kill notwithstanding he had five balls through his lungs and five others in various parts… it was at least twenty minutes before he died.”

Their documentation of various trees, plants, flowers, and shrubs all served to be of great value. In particular, with the help of Sacajawea Lewis and Clark made detailed notes of the edible plants for foraging as well as the best tree wood for use on wagons and transport.

The expedition collected so many samples that over their winter near the Pacific ocean they hoped to see a ship so they could send a man and make it easier to transport all their specimens back.3

Mapped route to Pacific Ocean

Another reason the Lewis and Clark expedition was so important was that it helped to map a viable route to the Pacific Ocean.

One of Jefferson’s stated goals for the expedition was to find an uninterrupted water passage to the Pacific. Such a route would prove enormously valuable for American commerce.

Unfortunately, no such route existed, despite Lewis and Clark’s laborious attempts to find one.2

Despite this failure maps and notes from the various members of the Corps of Discovery would prove enormously valuable over subsequent decades.

It was the daily custom of Lewis and Clark, as well as all of the officers to make rough notes as well as maps of the locations they passed through.4

Lewis and Clark Expedition map
William Clark’s track map via LOC

These maps and notes on routes, landmarks, friendly vs. hostile Native Americans, water sources, etc all served to greatly aid settlers in their trek west in the future. Their efforts surely helped families traveling along the Oregon Trail and prospectors making their way to the California gold fields in 1849-1850.

Some of the maps even turned out to be ahead of their time. Historians widely consider William Clark’s track map of the expedition’s route to be a landmark achievement in American cartography.3

Aside from the obvious value of maps and notes, the Corps of Discovery also helped identify locations for future settlements in the west as well as extended the range and trade relationships for the American fur trade.

Spurred Manifest Destiny

An influential result of the Lewis and Clark expedition undoubtedly lies in how it spurred the concept of Manifest Destiny in the United States.

While Napoleon’s decision to sell the Louisiana territory sparked a flame, Lewis and Clark’s journey and the tales they brought back with them captivated the nation.

Pioneers eagerly moved into the new territory settling further and further west, spurred on by the “untamed” land before them.

Artists followed in the aftermath of the expedition, drawing images of beauty and vast wilderness just waiting to be tamed. Settlers moved quickly with Louisiana and Missouri becoming the first states admitted into the Union from the Louisiana Purchase in 1812 and 1820 respectively.

Americans and foreigners alike eagerly awaited the publishing of Lewis and Clark’s journals upon their return.

Due to several delays, as well as Meriwether Lewis’ likely death by suicide in 1810, the journals were not published until 1814, nearly eight years after the end of the journey.

Lewis and Clark's Journals and Expedition

Clark entrusted a young, prominent Nicholas Biddle to publish the combined narrative. Biddle later gained notoriety as the President of the Second Bank of the United States during the 1832 Bank War with Andrew Jackson.

Biddle condensed nearly 1.2 million words from the two journals into a captivating ~370,000 word narrative across two volumes. The Biddle narrative went on to be reprinted into twenty distinct editions and was published around the globe.4

The tales of Lewis and Clark traveled ever further, sparking land hunger as they went. Eventually, many Americans believed it was the destiny of the United States to spread across the North American continent from the Atlantic to the Pacific.

Following the Treaty of Guadalupe Hidalgo with Mexico, the United States finally realized its Manifest Destiny ambitions.

Opened Diplomatic Relations with Native Americans

A final reason why the Lewis and Clark expedition was important was that it opened diplomatic relations with Native Americans of the Plains Nations.

The expedition came with messages of peace and dutifully gave out “peace medals” to the native tribes encountered. These medals served great purpose in native society, signifying cohesive trade relations and mutual protection.

However, Lewis and Clark were also sure to display American technological superiority and power. They carried high-powered rifles with them and even two blunderbusses used for short range combat that emitted great noise.

The expedition often fired weapons to signal their arrival to native villages. While some natives were familiar with gunpowder weapons, for others it was their first experience.

Lewis and Clark carefully documented all the nations they encountered, particularly the powerful ones that could someday pose a threat to the United States. The Lakota Nation in particular gave them pause. Lewis wrote:

“These were a savage race… we will make them feel the dependence on our will for their survival”

In their journals they intentionally craft a lie that the Lakota were not native to the land and recently moved onto it, despite their having lived there for centuries. Settlers and officials would later use that as a basis to force the Lakota off their lands and onto reservations.3

Lewis and Clark peace medal
The “peace medals” that Lewis and Clark brought with them via LOC

Lewis and Clark’s journals showcased how they saw themselves as superior to the “savages” of the plains.

Despite this, it’s often omitted from the history books that their expedition likely would have failed without native support. Numerous times the group ran low on provisions and natives helped supply and outfit them for the journey.3

When Sacajawea joined the group she provided invaluable knowledge of the wilderness and of edible plants along the route. Even just her presence in the group helped as a woman traveling with Lewis and Clark signaled their peaceful intentions.3

While Lewis and Clark succeeded with their diplomatic mission, it would come at the detriment to the Native American nations of the plains in the years to come.


To recap the Lewis and Clark expedition was important for the following four reasons:

  1. Discovered new plants and animals
  2. Mapped a new route to the Pacific Ocean
  3. Spurred Manifest Destiny in the United States
  4. Opened diplomatic relations with Native American Nations

Remarkably, after the initial fervor over the expedition, interest gradually waned. Biddle’s narrative of events published in 1814 satisfied scholars’ thirst for knowledge, and the original journals, maps, and notes sat forgotten.

Fortunately, Thomas Jefferson saw fit to collect the original documents for the American Philosophical Society in 1817. For nearly 75 years they lay virtually untouched in a vault of the society until renewed interest in the expeditions in the 1890-1900s.4

Since then Lewis and Clark have taken on an almost mythic persona in United States history. Schools around the nation highlight their journey and the significant impact it had on the nation.

The moment the Corps of Discovery set foot on their mission, the United States would be forever changed.


To learn more about US history, check out this timeline of the history of the United States.


1) Fresonke, Kris, and Mark Spence, editors. Lewis & Clark: Legacies, Memories, and New Perspectives. 1st ed., University of California Press, 2004. JSTOR, http://www.jstor.org/stable/10.1525/j.ctt1pnt2f.

2) Foley, William E. “Lewis and Clark’s American Travels: The View from Britain.” Western Historical Quarterly, vol. 34, no. 3, 2003, pp. 301–24. JSTOR, https://doi.org/10.2307/25047296.

3) Soldier, Lydia Whirlwind. “Lewis and Clark Journey: The Renaming of a Nation.” Wicazo Sa Review, vol. 19, no. 1, 2004, pp. 131–43. JSTOR, http://www.jstor.org/stable/1409490.

4) Thwaites, Reuben Gold. “The Story of Lewis and Clark’s Journals.” The Quarterly of the Oregon Historical Society, vol. 6, no. 1, 1905, pp. 26–53. JSTOR, http://www.jstor.org/stable/20609636.

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