The collection was started in the 1920s as a private collection by Heinrich, Baron Thyssen-Bornemisza de Kászon. In a reversal of the movement of European paintings to the US during this period, one of the elder Baron's sources was the collections of American millionaires coping with the Great Depression and inheritance taxes. In this way he acquired old master paintings such as Ghirlandaio's portrait of Giovanna Tornabuoni (once in the Morgan Library) and Carpaccio's "Knight" (from the collection of Otto Kahn). The collection was later expanded by Heinrich's son Baron Hans Heinrich Thyssen-Bornemisza (1921–2002), who assembled most of the works from his relatives' collections and proceeded to acquire large numbers of new works (from Gothic art to Lucien Freud).