Mellon served under presidents Harding, Coolidge and Hoover as Secretary of the Treasury, during which time he reduced U.S. debt by 9 billion dollars. .<ref>The New American Desk Encyclopedia, Penguin Group, 1989</ref> Mellon ranked, at the time, as one of the richest people in the world. His vast art collection formed the basis of the [[National Gallery of Art]]. | Mellon served under presidents Harding, Coolidge and Hoover as Secretary of the Treasury, during which time he reduced U.S. debt by 9 billion dollars. .<ref>The New American Desk Encyclopedia, Penguin Group, 1989</ref> Mellon ranked, at the time, as one of the richest people in the world. His vast art collection formed the basis of the [[National Gallery of Art]]. |