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. and Harriman Brothers & Co. formed the current BBH.

Brown Bros. & Co. was an investment bank from 1818 until its merger with Harriman Brothers & Company in 1931, to form Brown Brothers Harriman & Co. According to Zachary Karabell:In its first hundred years, the firm helped to make paper currency standard in the U.S., underwrote the earliest railroad and trans-Atlantic steamship companies and almost unilaterally created the first foreign exchange system between the American dollar and the British pound. In the 20th century, it became a cornerstone of what came to be known as “the Establishment,” as its partners entered the halls of government to shape the global economic and security system that remains the world’s institutional architecture.