"The case for raising rates has decreased somewhat", Fed chairman Jerome Powell said at a news conference following the rate announcement. That language had roiled markets amid signs of slower global growth. He has said the increases are hurting the stock market, which declined significantly at the end of 2018. "This marks a full 180 from what the Fed was signaling just a few months ago", he said. Amid the crosscurrents of a strong USA economy and some uncertainties overseas, a "common-sense" approach means the Fed will patiently await "greater clarity" and rely on economic data to guide policy, Powell said.
"The Fed refilled the punch bowl and the party goes on".
"Risk assets are dancing in the streets and the dollar's down in the dumps", Societe Generale strategist Kit Juckes said.
Powell will then give a news conference, beginning a policy of speaking with reporters after each of the Fed's eight meetings every year, rather than only four times a year.
The Nasdaq Composite added 1.31 percent to 7,277.26.
Boeing shares added 6.3 per cent, providing one of the largest boosts to the United States market, after the aerospace company posted strong quarterly earnings, which beat expectations.More news: Nintendo delays its very first Mario Kart game for mobile
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"Inflation is the main story, " said Neil Dutta, head of USA economics at Renaissance Macro Research LLC.
And don't forget that a delegation from China has arrived in the US for trade talks, And the outcome might even be more important than the Fed.
For January it is up more than 7.2 percent which is its best January since the index began in 1988 and the best performance in any month since December 2015.
Up almost 8 percent year to date, the S&P 500 is on track to post its best monthly performance since October 2015.
"The vote is not fundamentally changing the way the market's talking about Brexit", said Hetal Mehta, Legal & General Investment Management senior European economist.
Added together it lifted the $4 trillion MSCI world stocks index, which tracks 47 countries, up 0.5 percent and for the 20th day out of the last 23. The job market, for example, remains robust, with solid and steady hiring. Against the yen, the dollar fell 0.33 percent to 109.02.
Of the 210 S&P 500 companies that have reported fourth-quarter results, 71 percent have topped profit estimates, according to Refinitiv data. Crude rose as US sanctions against Venezuela threatened to disrupt the global supply backdrop while gold got a boost from a weakened USA dollar.
The influential energy and materials sectors led the way on higher crude oil and gold prices.