|Traders work on the floor of the New York Stock Exchange. (Bryan R. Smith/AFP)|
The record finishes for all three indices nevertheless capped a day of uncertain movement, with stocks opening lower before haltingly edging higher.
The Dow Jones Industrial Average rose 6.13 points (0.03 per cent) to 23,563.36, while the broader S&P 500 gained 3.74 points (0.14 per cent) to 2,594.38.
The tech-heavy Nasdaq saw stronger gains, adding 21.34 points (0.32 per cent) to settle at 6,789.12.
Investors marked a year since Trump's victory in the 2016 elections, sparked a Wall Street rally. The upbeat mood on the markets has sent the Dow and Nasdaq up about 30 per cent, and the S&P 500 up 20 per cent.
But analyst Hugh Johnson told AFP the fears about the fate of corporate tax cuts - a key plank of the Trump and Republican agendas - had blunted investor appetite.
The rally is "stalling out because there is still concerns of whether we will get cuts on corporate taxes," he said, so "The market becomes pretty trendless."
The Washington Post reported late Wednesday that Senate Republicans were considering delaying the rollout of its version of the tax plan, that had been expected Thursday, amid intense criticism of the House plan.
Meanwhile, sources confirmed to AFP that the US Justice Department told Time Warner to sell Turner Broadcasting, the group of cable channels including CNN, as a condition of its merger with the telecom giant AT&T.
AT&T finished up 1.2 per cent while Time Warner plunged 6.5 per cent on the news.
Shares in social media firm Snap nosedived 14.6 per cent a day after the company forecast slow revenue and user growth. The company also said China's Tencent had bought a 12 per cent stake in the company.