Controlled by the Paine family, in the 1920s, Paine, Webber & Co. entered the investment banking business. After nearly fifty years at the head of the company, the successful and wealthy William A. Paine died just weeks before the Wall Street Crash of 1929. His son, F. Ward Paine became head of the firm and the difficult years during the Great Depression of the 1930s saw Paine Webber merge with a brokerage firm owned by Charles Cabot Jackson and Laurence Curtis, creating "Paine, Webber, Jackson & Curtis" on June 29, 1942. The combined operation had twenty-three offices and with their greater asset base were a significant force in the New England financial market.
The partnership eventually reverted to the Paine, Webber name and in 1955 the last member of the Paine family to run the company died. At the time, Paine Webber was the fourth largest brokerage firm in the United States. Because of the importance of Wall Street, in 1963 the Board of Directors made the decision to move corporate headquarters to New York City. In 1972, Paine Webber became a publicly traded company, its shares listed on the New York Stock Exchange. With profitable growth and capital raised from its IPO, the company was able to make significant acquisitions over the ensuing two decades, most notably that of "Mitchell Hutchins" in 1977 which provided them with a major equity research base, plus "Blyth, Eastman Dillon & Co." in 1979.
By 1980 Paine Webber had 161 branch offices in 42 states and six offices in Asia and Europe. 1995 saw a significant expansion with the acquisition of the brokerage firm, Kidder, Peabody & Co. With a significant nationwide presence, and operating as PaineWebber Group Inc., by late 2000 they were the fourth largest private client firm in the United States with 385 offices employing 8,554 brokers.
On November 3, 2000, the company merged with UBS AG, a banking conglomerate headquartered in Zurich, Switzerland. Initially the business was given the divisional name "UBS PaineWebber" but in 2003 the 123-year-old name Paine Webber disappeared when it was renamed "UBS Wealth Management USA."