How Did the Lewis and Clark Expedition Affect American History?

The Lewis and Clark Expedition, also known as the Corps of Discovery Expedition, was a significant event in American history. Undertaken by Meriwether Lewis and William Clark from 1804 to 1806, this expedition explored the western territory of the United States and its impact is still felt today. Let’s take a closer look at how this expedition affected American history.


In the early 1800s, President Thomas Jefferson was eager to explore the western part of the United States. He commissioned Meriwether Lewis and William Clark to lead an expedition to find a water route to the Pacific Ocean. The Corps of Discovery was formed, consisting of around 50 men who would undertake this journey.

The Expedition

The Lewis and Clark Expedition began in May 1804 in St. Louis, Missouri. The group traveled up the Missouri River, through present-day Nebraska and South Dakota, then across Montana to reach the Pacific Ocean. Along the way, they encountered various Native American tribes, many of whom had never seen white men before.

Impact on Native Americans

The Lewis and Clark Expedition had a significant impact on Native American tribes in the western United States. While some tribes were friendly towards Lewis and Clark’s group and even helped them along their journey, others were not as welcoming. The expedition introduced many Native Americans to diseases they had never encountered before, which had devastating effects on their populations.

Discovery of New Species

During their journey through the wilderness, Lewis and Clark discovered many new plant and animal species that were previously unknown to science. They also documented detailed descriptions of these species in journals that are still studied today.

Expansion of American Territory

One of the most significant impacts of the Lewis and Clark Expedition was its role in expanding American territory. After their journey was complete, the United States government gained a better understanding of the western landscape and its potential for settlement. This knowledge paved the way for future westward expansion, which influenced American history for years to come.


The Lewis and Clark Expedition was a critical event in American history, with far-reaching impacts that are still felt today. From expanding American territory to discovering new plant and animal species, this expedition paved the way for future exploration and development of the western United States.