Commodore George Dewey during the Spanish-American war. He returned to America to a hero's welcome, and by act of Congress was promoted to the special rank of Admiral of the Navy in 1903 with his date of rank retroactive to 1899.
George Dewey was made Admiral of the US Navy on March 24, 1899. He is best known for his victory at the Battle of Manila Bay during the Spanish-American War. Read more: http://en.wikipedia.org/wiki/George_Dewey