Black October

October was a rough ride for U.S. stocks, which ended as one of the market's worst months since the financial crisis.The S&P 500 lost 6.9 percent in October, its biggest one-month slide since September 2011, when it fell 7.2 percent. The Nasdaq plunged 9.2 percent, its largest monthly pullback since November 2008, when it lost 10.8 percent.

The S&P 500 lost $1.91 trillion in value for the month, with widespread losses almost across the board. Consumer staples and utilities were the only major S&P 500 sectors in the black in October.

Big technology stocks, including the FAANG group, were among the hardest hit. Amazon ended the month down 20.2 percent, and Netflix ended down 19.3 percent. Facebook and Alphabet finished October down 7.7 percent and 9.7 percent, respectively.