October 19, 1987, has become the day known infamously as "Black Monday. It set forth a chain reaction of market distress that sent global stock exchanges plummeting in a matter of hours. In the United States, the Dow Jones Industrial Average (DJIA) dropped 22.6 percent in a single trading session. This loss remains the largest one-day stock market decline in history and marks the sharpest market downturn in the United States since the Great Depression.
The important significance of this event lies in the fact Black Monday underscored the concept of "globalization," which was still quite new at the time. The event demonstrated the extent to which financial markets worldwide had become intertwined and technologically interconnected. This led to several noteworthy reforms, including exchanges developing provisions to pause trading temporarily in the event of rapid market sell-offs. More importantly, it forever altered the Federal Reserve's response on how to use "liquidity" as a tool to stem financial crises.
Leading up to this event the stock markets raced upward during the first half of 1987 gaining a whopping 44 percent in just seven months. This, of course, created concerns of an asset bubble, however, few market traders expected the market could unravel so viciously.