October 19, 1987: As a call-back to the October 28, 1929 stock market crash on Black Tuesday, Black Monday refers to the October 19, 1987 stock market crash during which the Dow Jones Industrial Average (DJIA) fell 508 points (22.6% of its value) and the Dow Jones Index lost over $500 billion.
The impact of Black Monday was felt beyond DIJA; the NASDAQ and S&P 500 both reported record losses and countries beyond the United States (including Australia, Mexico, Singapore, and Hong Kong) also experienced crashes in their stock markets. Luckily, Black Monday did not lead to an economic downturn similar in scope to that of the Great Depression. In fact, just a few couple of years later, the Dow had fully recovered and reached record-breaking highs.
Source: Library of Congress Research Guide
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A first-class catastrophe: The road to Black Monday, the worst day in Wall Street history by Diana B. Henriques.