Richard Evelyn Byrd Jr. (October 25, 1888 – March 11, 1957) was an American naval officer and explorer. He was a recipient of the Medal of Honor, the highest honor for valor given by the United States, and was a pioneering American aviator, polar explorer, and organizer of polar logistics. Aircraft flights in which he served as a navigator and expedition leader crossed the Atlantic Ocean, a segment of the Arctic Ocean, and a segment of the Antarctic Plateau. Byrd said that his expeditions had been the first to reach both the North Pole and the South Pole by air. His belief to have reached the North Pole is disputed. He is also known for discovering Mount Sidley, the largest dormant volcano in Antarctica.