Stocks hit four-year highs after the European Central Bank laid out a concrete plan to support the region's struggling countries by buying bonds.
That set off a global market rally. The Dow Jones industrial average jumped 244.5 points to close at 13,292, its highest close since December 2007.
The Standard & Poor's 500 index soared 28.7 points to close at 1,432.1, the highest since January 2008.
The Nasdaq composite index jumped 66.5 points to 3,135.8, its highest level in 12 years.
ECB president Mario Draghi said the new program will have no set limit on the amount of government bonds it can buy.
Nearly four stocks rose for every one that fell on the New York Stock Exchange. Trading volume was 3.9 billion, above the recent average.