The Dow Jones Industrial Average surged more than 300 points to cross 21000 for the first time, as investors embraced optimism from President Donald Trump and Federal Reserve officials.

Stocks have soared since November, with the blue-chip index surpassing 19000, 20000—and now 21000. Investor enthusiasm for Mr. Trump’s plans to cut taxes, loosen regulations and ramp up fiscal spending have bolstered shares alongside signs of improvement in the U.S. economy.

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