Between May 1804 and September 1806, Meriwether Lewis and William Clark and their Corps of Discovery explored a new expanse of America known as the Louisiana Purchase. They encountered lands, rivers, and peoples previously unknown Americans east of the Mississippi. During the next sixty-five years, Lewis and Clark's journey was followed by other explorations of the West, from the Mississippi River to the Pacific Ocean and from Canada to Mexico. Artists often accompanied explorers as they encountered the unexpected and unique subjects of the American West. Inspired by the thrill of adventure and the majesty of high mountains, great chasms, and wide-open spaces, artists became eyewitnesses and visual commentators of the changing shape of the frontier--and the tragic displacement of American Indian tribes. As these artists sought to capture on paper and canvas what they saw during their explorations and travels, they gave birth to American western art.