It was the defining moment of the 1980s. The New York Stock Exchange, the epicenter of the world financial markets and backbone of American capitalism, was under siege. On October 19th, 1987, the Dow Jones Industrial Average plunged 508 points, the largest single day drop in the history of the stock market. But it was on Tuesday, October 20th that the world's financial markets came within 5 minutes of total disintegration.