President Donald Trump marked the 250th anniversary of American independence with a speech at Mount Rushmore that shifted sharply from celebratory patriotism into stark political warnings about communism.

“Communism is a mortal threat to American liberty,” Trump declared from the monument. “It is the greatest threat to our country, including World War I, World War II, Pearl Harbor or even 9/11.”

The remarks stood out for being delivered at a national park that commemorates some of the country’s most prominent presidents, rather than from a traditional political venue.

Trump’s language veered from the typically apolitical and unifying tone past presidents like Gerald Ford and Ronald Reagan adopted during high-profile Independence Day celebrations.

Many observers noted the speech evoked the Red Scare of the 1950s, when alleged communists were persecuted and blacklisted from jobs across America, from Washington to Hollywood.

In New York City, Mayor Zohran Mamdani, a democratic socialist, delivered a contrasting address that cast America as a nation of contradictions “working each day towards the perfection in which it was conceived.”

Mamdani did not mention Trump by name, but portions of his remarks appeared directed at the president’s rhetoric surrounding immigration and national identity.

“For generation after generation, we have been told that when the world has sent its people to our shores, it has not sent its best,” Mamdani said, in what appeared to be a reference to a common criticism from Trump.

“Those ideals upon which our nation was built — they are strong enough to endure any authoritarian regime, but only if we reach for them,” Mamdani added, in a remark widely interpreted as a pointed rebuke.

The political backdrop of Trump’s speech unfolded against a brutal heat wave gripping much of the eastern United States, forcing event organizers to make last-minute adjustments to holiday celebrations nationwide.

Philadelphia canceled its Salute to Independence parade, while the Great American State Fair in Washington shut down in the early afternoon before reopening at 5 p.m.

The Capitol Fourth concert in Washington moved forward despite the heat, featuring performances from Patti LaBelle, Trace Adkins, and members of the Artemis II space mission, capped with fireworks over George Washington’s Mount Vernon.

An Independence Day parade scheduled for Saturday in Washington was canceled, while festivities in cities across the country were curtailed or modified due to dangerous temperatures.

About 4 in 10 U.S. adults feel “proud” about the country’s 250th anniversary, according to an April survey from The Associated Press-NORC Center for Public Affairs Research, with roughly 3 in 10 describing their emotions as “excited.”

Freedom 250, an organization aligned with the White House, has emerged as a rival to America250, a bipartisan group founded by Congress a decade ago to oversee the anniversary celebrations.

Glenn Brooks, who was pardoned by Trump for his participation in the January 6, 2021, attack on the Capitol, attended the National Mall festivities and said he was “thankful to be participating in this grand event.”

Auto technician Joe Fuqua-Bejarano in Topeka, Kansas, reflected on what unites Americans, suggesting the answer lies not in politics but in resilience and a shared sense of humor.

“We’ve just all got to find unity somewhere, whether that’s in laughter or perseverance, and keep everybody cool,” he said from a fireworks stand he was operating as a side hustle.

Michael Dresdner, who traveled from West Orange, New Jersey, with a group that included people from both sides of the political aisle, offered a more optimistic assessment of the country’s future.

“We are all here, and we all love America,” he said, standing near the Declaration of Independence at the National Archives in Washington.