The event was delayed by nearly two hours after a storm threat forced the evacuation of the Mall, with visitors sheltering in nearby museums and government buildings before being allowed back once the danger passed.
Trump told the crowd about 375,000 people had been on site before the evacuation, with roughly 150,000 returning afterwards.
"If you think that was easy, it wasn't," he said, thanking those who stayed despite the lightning warnings.
Crowds had already spent hours queuing in record heat that reached 103°F (39°C), which also forced the cancellation of several other events in the area.
In a speech lasting under 40 minutes – far shorter than he had earlier suggested – Trump praised American milestones including war victories, the Moon landing and the Wright brothers' first flight, and called the US "stronger, freer, richer, safer and prouder than ever before."
He pushed Congress to pass the stalled "Save America Act," which would require voter ID and proof of citizenship and largely end mail-in voting except for illness, disability, military service or travel.
He also said he had "wiped out" Venezuela's and Iran's military.
On communism, he warned: "We like to stop a threat like that immediately and before it begins. It's like a cancer. You got to cut it out. You got to cut it out fast."
Trump has previously used "communists" to describe left-wing Democratic candidates, though he stopped short of naming them directly this time.
Veterans and astronauts joined him on stage, and the speech was followed by the national anthem and a fireworks display Trump had promised would be the biggest ever.
Unlike past presidents, who generally avoided in-person July 4 appearances, Trump has blurred the line between official commemoration and political rally – no sitting president had delivered a July 4 speech on the Mall since 1951, aside from Trump himself in 2019, the Reuters news agency noted.
Also present in Washington was the white nationalist group Patriot Front, which marched through the city and rode public transport; police reported no incidents of violence.
A politically charged anniversary
The celebrations, branded "Freedom 250," have largely sidelined the nonpartisan body originally set up in 2016 to organise the milestone.
Much of the Mall was fenced off for a "Great American State Fair" featuring a Ferris wheel alongside displays from conservative groups and defence contractors.
Several Democratic-led states skipped the festivities, and some scheduled performers withdrew citing concerns over partisanship.
Critics say accompanying "Freedom Trucks" present an overly religious version of American history that glosses over slavery and racial injustice.
A Reuters/Ipsos poll found that most Americans, including three-quarters of Democrats and half of Republicans, feel the anniversary celebrations have become too political.
Calls with Kyiv and Moscow
Separately, Trump spoke by phone on Saturday with both Ukrainian President Volodymyr Zelensky and Russian President Vladimir Putin.
Zelensky said on X the call was "very good," thanking the US for its support and saying "America's resolve will be decisive" in ending the war.
He said the two also discussed the front line and diplomatic efforts, and agreed to continue talks at next week's NATO summit in Ankara, Turkey.
According to Russian officials cited by Reuters, Putin's call with Trump lasted 85 minutes and covered the situation at the front, with the Russian president briefing the US leader on developments.
Trump reportedly again offered to help end the war and said he would raise it at the NATO summit.
Putin's foreign policy adviser, Yuri Ushakov, said US envoys Steve Witkoff and Jared Kushner would continue negotiating and were ready for another visit to Moscow, calling the call "business-like and quite constructive."
The calls came a day after Moscow claimed to have captured the town of Konstantinivka in Donetsk region and full control of Luhansk region – claims rejected by both Zelensky and Ukraine's General Staff.
(ał)
Source: PAP, Reuters