1931 January 1 W.A. Harriman & Co. merges with Brown Brothers.Prescott Bush, father of future President George Bush, becomes the managing partner of the new firm: Brown Brothers Harriman, ultimately the largest and most politically important private banking house in America. The London branch of the Brown family firm continued to operate under the name -- Brown, Shipley.

During the American Civil War (War of Southern Secession), the Brown family with offices in the U.S. and London shipped 75% of the South's slave cotton to British mills.