The hit an all-time high on Tuesday and tied the record for the longest bull market ever as investors bet that the strengthening economy and booming corporate profits seen under President Donald Trump's first two years would continue, despite recent trade battles.
The broad index rose 0.2 percent and reached an intraday record of 2,873.23, led by consumer discretionary and industrial. The S&P 500 surpassed 2,872.87, a high reached on Jan. 26. The index failed to post a record close, however, ending the session at 2,862.96.
The bull market turns 3,453 days old on Wednesday, which would make it the longest on record by most definitions. On Tuesday, it tied the one that ran from October 1990 to March 2000. The S&P 500 has risen more than 300 percent since hitting its financial crisis bottom on March 9, 2009. For the year, the index is up more than 7 percent.
"Nobody believed in this bull market and they still don't," said Marc Chaikin, CEO of Chaikin Analytics. Lots of people "were left so scarred by the crisis they didn't get on board."
Chaikin also said the bull run can continue: "We have an economy that is not overheated and rates are still low. Couple that with the fact that people keep finding reasons to hate this market, that is a perfect storm for more gains."
The Dow Jones Industrial Average gained 63.6 points to close at 25,822.29, just 3 percent below a record high, with Intel and Goldman Sachs leading the index. The Dow Transports hit its first intraday record high since Jan. 16.
The Nasdaq Composite outperformed, rising 0.5 percent to 7,859.17 as Micron and Netflix rose. The Nasdaq also closed less than 1 percent from reaching an all-time high. The Russell 2000, which is made up of small cap stocks, reached a record high.
Equities have been boosted by strong corporate earnings and solid economic growth this and last year. Since the start of 2017, the S&P 500 has risen more than 25 percent.
Quarterly earnings have grown at least 10 percent in five of the past six quarters, according to FactSet. This year, quarterly profits have risen at least 20 percent in the first two quarters. Meanwhile, the U.S. economy expanded by 4.1 percent in the first quarter, its best pace since 2014.
The strong corporate earnings, coupled with the solid economic growth, has been enough to partially offset worries over global trade, particularly as U.S.-China relations become more tenuous.
Trump is reportedly preparing to add tariffs on nearly half of Chinese imports this week. The new round of tariffs would come despite the expectation of restarted negotiations between the two largest economies of the world.
"The three Ts, Trump, tariffs and trade, are sort of a wet blanket on the embers of growth, but ... the market can still go higher," said Greg Luken, CEO of Luken Investment Analytics. "Bull markets don't die of old age; they die of euphoria and we're nowhere near euphoria."
Quincy Krosby, chief market strategist at Prudential Financial, told CNBC that the market wants to go up. She added, however: "You still have hovering over the markets issues that could cause fundamental change – and above all else it is the Fed."
Trump went after the Federal Reserve once again, saying Monday he disagrees with the Fed's current tightening path for monetary policy. The Fed has already raised rates twice this year and is expected to raise rates two more times. Trump's comments, which weighed on interest rates on Monday, come shortly ahead of Fed Chair Jerome Powell's speech at Jackson Hole on Friday.
The dollar reached intraday lows on Monday after Trump's comments, continuing to fall 0.7 percent on Tuesday.
"If the inflation data dictates higher rates and the Fed instead buckles to political pressure and doesn't respond, long term rates will tighten for them," said Peter Boockvar, chief investment officer at Bleakley Advisory Group, in a note. Just "ask the Turkish central bank."
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Prudential's Krosby added that "this is a low volume period in the market," saying the months of August and September "tend to be choppy" due to stocks being "jostled very quickly by a single headline." With "so many threads" possibly moving stocks – whether it is the Fed, trade, the bull run or banks – Krosby says the market "is hedging itself." Traders are making defensive moves, in Krosby's view, as she sees a shift from technology stocks into more durable areas like health care, pharmaceuticals, telecom and utilities.