Brown Brothers Harriman, still in business, banker to Nazis since ? Forever. Officially 1931, before then it was Brown Bros & Harriman pre-merger
"Brown Brothers Harriman & Co. (BBH) is the oldest and one of the largest private investment banks in the United States. In 1931, the merger of Brown Brothers & Co. (founded in 1818) and Harriman Brothers & Co. formed the current BBH.
Brown Brothers Harriman is also notable for the number of influential American politicians, government appointees, and Cabinet members who have worked at the company, such as W. Averell Harriman, Prescott Bush, Robert A. Lovett, Richard W. Fisher, Robert Roosa, and Alan Greenspan."