Mellon's national reputation collapsed following the Wall Street Crash of 1929 and the onset of the Great Depression. Mellon participated in various efforts by the Hoover administration to revive the economy and maintain the international economic order, but he opposed direct government intervention in the economy. After Congress began impeachment proceedings against Mellon, President Hoover shifted Mellon to the position of United States ambassador to the United Kingdom. Mellon returned to private life after Hoover's defeat in the 1932 presidential election by Franklin D. Roosevelt. Beginning in 1933, the federal government launched a tax fraud investigation on Mellon, leading to a high-profile case that ended with Mellon's exoneration. Shortly before his death, in 1937, Mellon helped establish the National Gallery of Art, a national art museum. His philanthropic efforts also played a major role in the later establishment of Carnegie Mellon University and the National Portrait Gallery.