"I certainly view this as a slightly hawkish statement that the Fed added the word 'some' (versus 'further') improvement in the labor market," said Eric Lascelles, chief economist at RBC Global Asset Management. "The market has not been overwhelming in its response. (There's) some focus on oil."
Crude oil settled 81 cents higher at $48.79 a barrel. Earlier, oil briefly traded above $49 a barrel after the weekly crude inventories showed a greater-than-expected decline. Gold settled down $3.60 at $1,092.60 an ounce.
Energy jumped more than 1 percent to lead all 10 sectors in the S&P 500 higher, with the oil and gas drilling sub sector leading gains.
Read MoreOil stocks rally after inventory data
The Federal Open Market Committee concluded its two-day meeting in the afternoon and was scheduled to release its statement at 2:00 p.m. No press conference was planned.
"Once again Janet Yellen pulls off a dovish statement, the market likes it, and (it) doesn't take September off the table," said Doug Cote, chief market strategist at Voya Investment Management.
The 10-year Treasury yield briefly climbed to 2.3 percent before retreating to an earlier level of 2.28 percent. The 2-year yield was 0.70 percent, little changed from earlier levels.
"I think the market will quickly look past this Fed statement and focus on those things it's been looking at—oil prices, commodity prices, and the path China will take in the next couple of months," said Roger Bayston, director of fixed income at Franklin Templeton.
After initially trading flat, the dollar strengthened against major world currencies, with the euro falling below $1.10 and the yen slightly weaker at 123.9 yen against the greenback.
Read MoreHere's what changed in the new Fed statement
Earlier, the Dow Jones industrial average traded more than 100 points higher, led by gains in Microsoft, Verizon and Boeing. On Wednesday, Microsoft launched its latest operating system, Windows 10, its first free upgrade for some Windows users.
Stocks are higher on the "reversal in commodities, reversal in China, and an earnings season that continues to be reasonably good," Ben Pace, chief investment officer at HPM Partners, said ahead of the statement release. He expected a September rate hike.
"I think for the first time it's been a stock picker's market," he said.
Tableau plunged nearly 19 percent despite reporting earnings that beat on both the top and bottom line. Shares of big data analytics firm Splunk declined 4 percent in sympathy.
FBR Capital Markets said Tableau delivered a solid June quarter and maintained a "market perform" rating on the stock.
In economic news, pending home sales came in down 1.8 percent in June from May. Housing data so far has been mixed. Last week's new home sales report disappointed analysts while existing home sales jumped to an 8-1/2-year high.
Weekly mortgage applications barely moved for the second week in a row, rising just 0.8 percent, the Mortgage Bankers Association (MBA) said.
Earnings expected after the bell included Facebook, MetLife, Samsung Electronics, Marriott, Western Digital, and Whole Foods.
After the close Tuesday, Twitter reported earnings that beat on both the top and bottom line. However, user growth figures proved disappointing to investors, sending its shares sharply lower in after-hours trade. The stock closed down 14.5 percent Wednesday.
Gilead Sciences jumped 2.3 percent after it reported adjusted quarterly profit of $3.15 per share, outdistancing estimates of $2.71. Revenue also came in well above Street forecasts, with the drug maker benefiting from increased sales of hepatitis C treatments. Gilead also raised its full-year outlook.
Yelp missed on earnings per share but topped revenue expectations. The consumer review website gave a lower-than-expected forecast for current quarter revenue, amid increasing competition. Shares plunged 25 percent Wednesday.
Express Scripts fell about 1.2 percent after the firm topped earnings estimates and raised its full-years earnings forecast, but missed revenue expectations.
Read MoreEarly movers: HLT, ANTM, ETN, TWTR, GSK, GD & more
Hilton Worldwide posted earnings that beat estimates on earnings in-line with expectations. The hotel operator also said comparable property revenue per available room—a key hotel industry metric—should rise between 4.5 percent and 6.5 percent for the current quarter. The stock closed up 4.6 percent.