The ECB will buy 60 billion euros worth of assets a month, more than markets had been hoping for, in a program that will last through September 2016.
The choppiness seen early during the Wall Street session was due to some lingering questions about the effect of the announced measures on U.S. markets, said David Lebovitz, Global Market Strategist for J.P. Morgan Asset Management.
But as investors digested the details of the program it became more clear that the ECB was accomplishing exactly what it intended to.
This is really the bazooka people had been looking for in the past years, Lebovitz said.
He said the sectors most likely to gain from the ECB move would be anything that benefits from a stronger European economy, with bank and other cyclical stocks leading.
Banks led gains Thursday with the S&P 500 financials up 2.45 percent.
Wells Fargo (WFC) and Bank of America (BAC) rose 3.2 percent and 4.4 percent, respectively.
The Dow Jones industrial average (^DJI) rose 259.7 points, or 1.48 percent, to 17,813.98, the Standard & Poors 500 index (^GPSC) gained 31.03 points, or 1.53 percent, to 2,063.15 and the Nasdaq composite (^IXIC) added 82.98 points, or 1.78 percent, to 4,750.40.
Shares in Europe jumped 1.6 percent to close at a seven-year high.
After the closing bell, Starbucks (SBUX) shares rose 3.2 percent to $ 85.41 after sales at established restaurants in its Americas region were slightly stronger than analysts estimate.
American Express (AXP) was the largest points weight on the S&P 500, down 3.8 percent to $ 84.37, a day after it said it would cut more than 4,000 jobs this year as expenses and provisions for bad loans rose.
F5 Networks (FIVE) slumped 10 percent to $ 113.40. The network equipment-makers revenue missed expectations for the first time in eight quarters. It also forecast current-quarter revenue and profit below estimates.
Avon Products (AVP) shares jumped as much as 20.1 percent after Dealreporter said the company was in talks with private-equity firm TPG Capital about a potential transaction, citing three industry sources. Avon shares closed up 14.6 percent at $ 8.66.
Volume was slightly above the norm with about 7.7 billion shares changing hands on U.S. exchanges, above the daily average of 7.27 billion so far this month.
NYSE advancing issues outnumbered decliners 2,428 to 651, for a 3.73-to-1 ratio; on the Nasdaq, 2,015 issues rose and 746 fell, for a 2.70-to-1 ratio.
The S&P 500 was posting 78 new 52-week highs and 5 new lows; the Nasdaq composite was recording 61 new highs and 73 new lows.