The Nasdaq breached the 6,000 mark for the first time ever, spurred by a raft of strong corporate earnings and President Donald Trump's promise of a major tax reform plan.
The tech-heavy Nasdaq achieved the milestone thanks, in part, to strong gains by Biogen and Apple.
The index first breached the 5,000 mark on March 7, 2000 and closed above that level two days later during the height of the tech boom.
Biogen's shares jumped more than 4% after the biotech company reported better-than-expected quarterly profit and revenue.
Donald Trump promised last week to make "a big tax reform and tax reduction" announcement on Wednesday.
The US president has directed his aides to move quickly on a plan to cut the corporate income tax rate to 15% from 35%, a Trump administration official said yesterday.
Today's gains build on a day-earlier rally, which was driven by the victory of centrist candidate Emmanuel Macron in the first round of the French presidential election.
Polls show Macron is likely to beat his far-right rival Marine Le Pen in a deciding vote on May 7.
At the closing bell, the Nasdaq Composite Index stood at 6,025.68, up 0.7%.