NYSE Feb 28 2012
The floor of the New York Stock Exchange. Reuters

U.S. stocks soared Wednesday after the Federal Reserve surprised investors and analysts by extending rather than curtailing its unprecedented expansion of the money supply.

The S&P 500 index of large-capitalization stocks closed at a record high of 1725.52, while the Dow Jones Industrial Average of 30 blue-chip industrial stocks added 147,21 points to finish at a record 15,676.94.

The Fed's announcement Wednesday that it would not reduce its $85 billion-per-month purchases of Treasurys and mortgage-backed securities stunned Wall Street, which had thought the only question was whether the U.S. central bank would trim such purchases by $10 billion per month or $15 billion per month. The Fed's balance sheet is now approximately $3.66 trillion, more than it has ever been.

Treasury prices also climbed, as did gold -- up more than 4 percent -- and crude oil futures. The dollar fell to a nearly seven-month low against the euro.