U.S. stock indices closed mixed on Monday amid extreme volatility in the week's opening session, following a sharp early decline, a sudden strong rally, another downturn, and ultimately divergent performances.

Key index movements:

• The broad-market S&P 500 fell 11.83 points (0.23%)

• The Dow Jones Industrial Average dropped 349.26 points (0.91%)

• The Nasdaq Composite gained 15.48 points (0.10%)

Market context:
Today's trading occurred as the White House maintained its stance, even after President Donald Trump's imposition of shockingly high tariffs on most of America's major trading partners triggered market collapses across multiple exchanges, according to CNBC.

1. "Wall Street's rollercoaster session saw early plunges, a surprise rebound, and eventual divergence, with the Dow sinking 0.9% while Nasdaq eked out a 0.1% gain amid ongoing trade war tensions."

2. "Markets whipsawed violently before settling mixed, reflecting investor whiplash after Trump's aggressive tariffs rattled global commerce, with sector performances varying widely."