Lewis and Clark Expedition

Corps of Discovery meet Chinooks on the Lower Columbia, October 1805
"The Lewis and Clark Expedition from August 31, 1803, to September 25, 1806, also known as the Corps of Discovery Expedition, was the first expedition to cross the western portion of the United States. ... The Corps of Discovery was a select group of U.S. Army and civilian 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 American Indian tribes. The expedition returned to St. Louis to report its findings to Jefferson, with maps, sketches, and journals in hand. ..."
Wikipedia, W - List of species described by the Lewis and Clark Expedition (174 plants and 134 species and subspecies of animals, etc.), W - Sacagawea
Lewis and Clark: A Timeline of the Extraordinary Expedition
Discovering Lewis & Clark
YouTube: 23rd March 1806: The Lewis and Clark Expedition begins its return journey, Lewis and Clark | A film by Ken Burn, Lewis and Clark: Meriwether Lewis and William Clark (FULL Audiobook)

A map depicting the route taken by Lewis and Clark on their first expedition from the Missouri River (near St. Louis, Missouri) to the mouth of the Columbia River (at the Pacific Ocean in Oregon), and their return trip, 1804 - 1806.