It's October, season of fall harvests, MLB playoffs—and losing your shirt in the market. October accounts for five of the 10 biggest one-day declines ever by the S&P 500 (launched in 1957). So it's a good time to recall just how hysterical things can become when stocks get spooked. Here are the 10 worst trading days in S&P 500 history.
Date: Oct. 19, 1987