Investors reacted to the Federal Reserve's decision to leave rates unchanged, by handing the S&P 500 its biggest percentage gain for a Fed day since last July. The Nasdaq Composite had its best Fed day since Nov.

Wall Street's major averages moved higher on Wednesday as traders turned their attention to the Federal Reserve's rate decision slated to come later in the day. Early on and the S&P 500 (SP500) was +0.