The Lewis and Clark Expedition from May 1804 to September 1806, also known as the Corps of Discovery Expedition, was the first American expedition to cross what is now the western portion of the United States. Louis, made its way westward, and passed through the continental divide to reach the Pacific coast.The Corps of Discovery comprised a selected group of U. Army volunteers under the command of Captain Meriwether Lewis and his close friend, Second Lieutenant William Clark.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 Native American tribes.With maps, sketches, and journals in hand, the expedition returned to St. According to Thomas Jefferson himself, one goal was to find "the most direct and practicable water communication across this continent, for the purposes of commerce." Jefferson also placed special importance on declaring U. sovereignty over the land occupied by the many different tribes of Native Americans along the Missouri River, and getting an accurate sense of the resources in the recently completed Louisiana Purchase.Lewis and Clark began to gain new attention around the start of the 20th century.Both the 1904 Louisiana Purchase Exposition, in St.Louis, and the 1905 Lewis and Clark Centennial Exposition, in Portland, Oregon, showcased Lewis and Clark as American pioneers.
For years, Jefferson had heard of and read accounts of the various ventures of other explorers in parts of the western frontier and consequently had a long-held interest in further exploring this largely still unknown region of the continent.
In the 1780s, while Minister to France, Jefferson met John Ledyard in Paris and discussed a proposed trip to the Pacific Northwest.
Jefferson had also read Captain James Cook's A Voyage to the Pacific Ocean (London, 1784), an account of Cook's third voyage, and Le Page du Pratz's The History of Louisiana (London, 1763), all of which greatly influenced his decision to send an expedition.
Like Captain Cook, Jefferson also wished to discover a practical route through the Northwest to the Pacific coast.
Alexander Mackenzie had already charted a route in his quest for the Pacific, first following the later-named Mackenzie River to the Arctic Ocean in 1789.
Mackenzie and his party then became the first on record to cross America north of Mexico to the Pacific, when he arrived near Bella Coola in 1793—a dozen years before Lewis and Clark.