BY JONATHAN CHENG

After recovering a string of market milestones lost during the financial crisis, the Standard & Poor's 500-stock index is now speeding toward its next landmark.

At its close Tuesday of 1324.57, the S&P 500 is just points away from doubling off its 666.79 intraday nadir, reached in the darkest moments of the financial crisis in March 2009.

The index still needs a boost of about 0.7% to get over that symbolic hump. But, if it does so in the coming days, the S&P 500 will have doubled at the quickest pace since it rocketed to 16.15 from 8.06 in 1936.