Lewis and Clark's expedition, under the direction of Thomas Jefferson, mapped large areas of the Louisiana Purchase, searched for the Northwest Passage, and contributed significantly to the United States' geographic and scientific knowledge of the Western territories.
The lands explored by Meriwether Lewis and William Clark, often referred to as the Corps of Discovery, cover a significant portion of the modern United States. Commissioned by President Thomas Jefferson in 1803, their exploratory mission embarked in 1804 from St. Louis, Missouri, traversing westward across the continent to the Pacific Ocean. Along their journey, which lasted until 1806, they meticulously mapped the new territories of the Louisiana Purchase and sought a direct water route—the fabled Northwest Passage—to enhance trade with Asia. Despite not finding this non-existent passage, the expedition mapped vast expanses of the unknown west, documented diverse native flora and fauna, and established diplomatic relations with various Native American tribes. Their comprehensive reports and maps substantially enhanced the geographical knowledge of the United States and solidified American claims to the newly acquired lands.