The Dow Jones Industrial Average fell more than 610 points, or about 3.4%, on news of the U.K. vote to leave the EU.
By comparison, the Dow fell 508 points on Oct. 19, 1987, nicknamed "Black Monday." And on Sept. 29, 2008, the index fell 778 points, after the House of Representatives initially failed to pass the Bush Administration's proposed bank bailout plan. Of course, it's difficult to predict whether markets will resume their decline on Monday.
The S&P 500 also fell about 3.6% and the Nasdaq was down more than 4.1% at Friday's close. It was a particularly bad day for financial stocks, which saw their worst trading session since 2011, CNBC reports.
Oil also fell about 4.9%, though gold was trading up about 4.7% and bitcoin, that more modern alternative to traditional investments, was up more than 4.5%.