The four living former US presidents shared messages to mark the anniversary. Joe Biden recalled the Independence Declaration's edict that all people were created equal.

"We chose that path 250 years ago but that's where the work began, not where it ended," he said, adding that the nation's promise of equality for all was a work in progress.

The country's first black president, Barack Obama, reshared excerpts of a recent speech he made at his presidential museum's opening in June, when he had said "every generation must take up the unfinished work of the last and carry it further".

George W Bush said "the next 250 years require Americans to be citizens, not spectators".

Meanwhile, his predecessor, Bill Clinton, took a moment to comment on US politics today.

"Today, we celebrate this milestone amid another period of deep division, renewed questions about America's future and role in the world, and serious threats to our own institutions and to our democracy itself," he said.

Additional reporting by Kwasi Asiedu

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