The benchmark index is up 16 points, or 1 per cent, at 1,585, breaking its high of 1,576 set before the financial crisis.
Other indexes also rose Wednesday, led by technology stocks.
The Dow Jones industrial average rose 125 points, or 0.9 per cent, to 14,799. The Dow was on its way to another record high close, having set its latest one the day before. Intel was the biggest gainer in the Dow, up 3 per cent.
The Nasdaq composite index, which is heavily weighted toward technology stocks, rose even more than the Dow and S&P. The Nasdaq rose 1.6 per cent, or 52 points, to 3,290.