On August 31, 1803, U.S. Army Captain Meriwether Lewis and Lieutenant William Clark led the first United States expedition across the West to the Pacific Ocean that changed the course of American history.

President Thomas Jefferson commissioned Lewis and Clark for the expedition through funds associated with the recently acquired territory of the Louisiana Purchase. Jefferson created and commissioned a group called the Corps of Discovery and selected Meriwether Lewis as its leader. Lewis and Jefferson were friends and both Virginians. Lewis then selected Clark, another Virginian, who he had befriended in the Army.

Jefferson had many purposes in commissioning the Lewis and Clark expedition. Jefferson wanted to promote American western expansion, advance geographical knowledge of the West, determine if there was a Northwest Passage to Asia, find the best fur trade routes, gain a better understanding of the boundaries of the Louisiana Purchase, report on all scientific discoveries, and develop relationships with the native American Indians in the regions. Jefferson provided Lewis and Clark the best supplies available and instructed them to record all their observations.

On this day, August 31, 1803, Lewis and Clark set out on their journey from Pittsburg, Pennsylvania. Lewis wrote in his journal on that day, "Left Pittsburgh this day at 11 with a party of 11 hands 7 of which are soldiers, a pilot and three young men on trial they having proposed to go with me throughout the voyage." Lewis and Clark would eventually set up their "Camp River Dubois," i.e. team for the exploration, just north of St. Louis, Missouri.

Lewis and Clark’s team numbered over 40 individuals, including other soldiers, a French-Indian interpreter, and one slave. Lewis and Clark, though interested in many of the purposes of their trip such as science, geography, and history, were not intellectuals. However, they were very resourceful men that knew how to survive in the wilderness, deal with Native American Indians, and lead men.

From 1803 to 1806, Lewis and Clark averaged around 10-15 miles per day, fought off injuries, heat, insects, very difficult terrain, dealt with Indians, and logged all of their findings. Their unyielding efforts were followed by all Americans, and the world.

Upon completion of their expedition, Lewis and Clark traveled over 8,000 miles in just under 2 ½ years, lost only one member of their team, and made great discoveries in nearly all aspects of human knowledge about the West. Their expedition was extremely successful and sparked further wonder, amazement, and expansion into America’s West frontier.