Andrew William Mellon (March 24, 1855 – August 26, 1937), known also as A. W. Mellon, was an American banker, businessman, industrialist, philanthropist, art collector, and politician. The son of Mellon family patriarch Thomas Mellon, he established a vast business empire before moving into politics. He served as United States Secretary of the Treasury from March 9, 1921, to February 12, 1932, presiding over the boom years of the 1920s and the Wall Street crash of 1929. A conservative Republican, Mellon favored policies that reduced taxation and the national debt of the United States in the aftermath of World War I. Mellon also helped fund and manage Kennywood Park in West Mifflin, Pennsylvania.
Andrew began working at his father's Pittsburgh, Pennsylvania, bank, T. Mellon & Sons, in the early 1870s, eventually becoming the leading figure in the institution. He later renamed T. Mellon & Sons as Mellon National Bank and established another financial institution, the Union Trust Company in Pittsburgh in 1889. By the end of 1913, Mellon National Bank held more money in deposits than any other bank in Pittsburgh, and the second-largest bank in the region was controlled by Union Trust.