who led the 1st expedition to cross what is now the western portion of the united states
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 the western portion of the United States. It began near St. Louis, made its way westward, and passed through the Continental Divide of the Americas to reach the Pacific coast. The Corps of Discovery was a selected group of US Army volunteers under the command of Captain Meriwether Lewis and his close friend Second Lieutenant William Clark.