The Overland Expedition of Lewis and Clark


The Lewis and Clark Expedition from May 1804 to September 1806, also known as the Corps of Discovery, was the first American expedition to cross the western portion of the United States. It began in St. Louis, Missouri, made its way westward, and passed through the Continental Divide of the Americas to reach the Pacific coast. The Corps of Discovery was a selected group of US Army volunteers under the command of Captain Meriwether Lewis and his close friend Second Lieutenant William Clark.

U.S. President Thomas Jefferson commissioned the expedition shortly after the Louisiana Purchase in 1803 to explore and to map the newly acquired territory, to find a practical route across the western half of the continent, and to establish an American presence in this territory before Britain and other European powers tried to claim it. The campaign’s secondary objectives were scientific and economic: to study the area’s plants, animal life, and geography, and to establish trade with local American Indian tribes. The expedition returned to St. Louis to report its findings to Jefferson, with maps, sketches, and journals in hand.

Both during their journey westward to the Pacific and eastward home, Lewis and Clark would travel together and at times travels apart. Both men traveled entirely together in 1804 to the bend of the Missouri River. In 1805 and 1806 however they traveled both together and at times separately. Therefore the total distance traveled by both during the overall trip varied along with the terrain both explored.

GroupDistance Traveled in 1804 (km)Distance Traveled in 1805 (km)Distance Traveled in 1806 (km)
Meriwether Lewis and William Clark2189
Meriwether Lewis37574963
William Clark38725173

Of the 3757 km traveled by William Clark and the 3872 km traveled by Meriwether Lewis in 1805, 2542 km of it were traveled in each other’s company. Of the 4963 km traveled by William Clark and the 5173 km traveled by Meriwether Lewis in 1806, 3297 km of it were traveled in each other’s company.