S&P 500 dropped 19.04 points, or 1.39 percent, to 1,355.49. The Nasdaq Composite lost 37.08 points, or 1.29 percent, to 2,846.81.
Both the Dow industrials and the Nasdaq ended at their lowest levels since late June.
The S&P 500 has fallen 5.1 percent in the six sessions since election night. Wednesday marked the benchmark index's lowest close since July 25.
The Russell 2000 tumbled 2 percent. The Dow Jones Transportation average slid 2.6 percent. FedEx Corp shares dropped 3.7 percent to $87.12. Bank of America shares lost 3.6 percent to $8.99.
In contrast, Facebook shares jumped 12.6 percent to $22.36 as investors were relieved that expiring trading restrictions on a huge block of shares did not trigger an immediate wave of insider selling.
Teen clothing retailer Abercrombie & Fitch Co jumped 34.4 percent to $41.92 after the company reported unexpectedly improved third-quarter results and a full-year outlook that exceeded Wall Street's forecasts.
About 7.53 billion shares changed hands on the New York Stock Exchange, the Nasdaq and NYSE MKT, more than the daily average so far this year of about 6.51 billion shares.
On the NYSE, decliners outnumbered advancers by a ratio of almost 9 to 1. On the Nasdaq, about four stocks fell for every one that rose.