The Corps of Discovery were the first U.S. citizens to reach the Northwest by land, strengthening the American claim established in 1792 when mariner Robert Gray discovered the Columbia River. When Lewis unfurled the Stars and Stripes, he made two different statements. To the Lemhi Shoshone people who lived here, the flag introduced a new nation to a remote tribe never before visited by Euro-Americans. For America's European rivals in the region—Spain, Russia, and Great Britain—Lewis's flag was another red, white and blue pin on the map.