US stock indexes posted strong gains on June 18, 2026, powered by a semiconductor rally and renewed optimism around a US-Iran peace deal. The Nasdaq composite led the way, climbing 1.9%, while the S&P 500 gained more than 1% and the Dow posted a more modest advance.
The real star of the session was the chip sector. The Philadelphia Semiconductor Index, the benchmark tracker for the industry, surged 6.4%. Intel shares jumped 10.6% to hit an all-time closing high.
Chips and diplomacy: the twin catalysts
Two forces converged to push equities higher. The first was a geopolitical breakthrough: the US and Iran signed an interim peace agreement extending a previous ceasefire by an additional 60 days. Lower geopolitical risk typically translates into lower oil prices, which eases inflationary pressure.
The second catalyst was domestic. President Donald Trump announced a collaboration between Apple and Intel focused on US-based chip design and manufacturing capabilities.
