Global stocks and the pound plunged after Britons voted to leave the European Union.
The Dow Jones industrial average dropped 611 points, or 3.4 percent, to 17,399 in heavy trading Friday.
The Standard & Poor's 500 index fell 75 points, or 3.6 percent, to 2,037. The Nasdaq composite sank 202 points, or 4.1 percent, to 4,707.
It was the biggest drop for the Dow and S&P 500 since August and the worst fall for the Nasdaq since 2011.
Some European markets fell even more. France's benchmark index lost 8 percent and Germany's fell 7 percent. Britain's fell 3 percent. Bond prices rose sharply as investors sought safety.
The yield on the 10-year Treasury note dropped to 1.57 percent from 1.75 percent a day earlier, a huge move.
"People don’t realize how global this will be, it destabilizes the entire political order in Europe ," said Nashville resident and musician John Wheeler who is currently living in England.
Wheeler is concerned that with Britain leaving the EU it will be tougher for his band to travel freely to other countries in Europe.
"Nobody’s quite sure how do it because nobody has ever done it," he added.