In 1919 , Kennedy joined the prominent stock brokerage firm of Hayden , Stone & Co. where he became an expert dealing in the unregulated stock market of the day , engaging in tactics that were later considered to be insider trading and market manipulation . He happened to be on the corner of Wall and Broad Streets at the moment of the Wall Street bombing on September 16 , 1920 , and was thrown to the ground by the force of the blast . In 1923 , he left Hayden and set up his own investment company . Kennedy subsequently became a multi-millionaire during the bull market of the 1920s and even wealthier as a result of taking " short " positions in 1929
Wall Street bombing
Wall Street bombing
Joseph P. Kennedy Sr.