The S&P 500 jumped past the 4,000 mark for the first time on Thursday, riding gains in Microsoft, Amazon and Alphabet, as well as optimism about a recovering U.S. economy.
Microsoft, Amazon, Alphabet and Nvidia jumped 1pc or more, with those and other growth stocks showing signs of awakening after lagging in recent weeks behind so-called value stocks expected to outperform as the economy recovers from the coronavirus pandemic.
Data showed the number of Americans filing new claims for unemployment benefits rose unexpectedly last week.
However, other data showed a measure of manufacturing activity soared to its strongest level in more than 37 years in March, with employment at factories the highest since February 2018.
In afternoon trading, the Dow Jones Industrial Average was up 0.5pc at 33,145.88 points, while the S&P 500 gained 0.95pc to 4,010.77.
The Nasdaq Composite added 1.48pc to 13,442.31.
With its latest intra-day record, the S&P 500 was up about 7pc in 2021, and has gained about 80pc from its low in March 2020.
"We're still bullish for this year, and we think that with stimulus, with the Fed committed to being dovish, with the economy reopening due to more of the U.S. getting vaccinated, overall you're going see corporate earnings do pretty well," said King Lip, chief investment strategist at Baker Avenue Asset Management in San Francisco.
The Nasdaq remained about 5pc below its Feb. 12 record high close, still smarting as higher U.S. bond yields hurt technology stocks.
Nine of the 11 major S&P sectors rose, with technology, communication services and energy gaining more than 1pc.
Micron Technology Inc jumped 4pc after the chipmaker forecast fiscal third-quarter revenue above Wall Street estimates due to higher demand for memory chips, thanks to 5G smartphones and artificial intelligence software.
U.S.-listed shares of rival Taiwan Semiconductor rose 3.7pc after it said it will invest $100 billion over three years to meet rising chip demand.
The three main indexes are set to close out a holiday-shortened week with gains, led by the Nasdaq. U.S. stock markets will close for the Good Friday holiday.
The CBOE volatility index slipped below 18 points for the first time in 14 months, a level last seen before the coronavirus-driven global financial market meltdown in March 2020.
Johnson & Johnson fell 0.5pc after the drugmaker said it had found a problem with a batch of the drug substance for its COVID-19 vaccine being produced by Emergent Biosolutions, whose shares tumbled 14pc.
Advancing issues outnumbered declining ones on the NYSE by a 3.42-to-1 ratio; on Nasdaq, a 2.66-to-1 ratio favored advancers.
The S&P 500 posted 25 new 52-week highs and no new lows; the Nasdaq Composite recorded 73 new highs and 11 new lows.