The phrase "a crowd assembled" is correct and usable in written English.
It can be used to describe a gathering of people coming together in one place, often for a specific purpose or event.
Example: "As the concert began, a crowd assembled outside the venue, eagerly waiting to enter."
Alternatives: "a gathering formed" or "a group gathered".
"There is a crowd assembled outside, they've come to gawk.
"There is not enough money, not enough money for us to live," she said as a crowd assembled.
At midday, Washington took his oath standing on a balcony above a crowd assembled on Wall Street.
A crowd assembled, some coming from the tent city, some with lunch from food trucks at the farmer's market.
They're not listening to what you need," he told a crowd assembled at a rodeo site in Fort Madison on a recent evening.
A crowd assembled at the America's Cup Park, a temporary theme park of a village that includes shops, bars and an outdoor concert venue.
On a nearly cloudless day in late January, Newt Gingrich stood in front of the P.G.A. Museum of Golf, in Port St. Lucie, Florida, and addressed a modest crowd assembled on a putting green.
Although we have heard the word 'gibbon' since olden times and seen pictures of him, we never had seen a live specimen, and therefore a large crowd assembled to see this gibbon.
We're nearing the end of April, so it seems suitable to address the end of "A Visit from the Good Squad" — the final chapter, "Pure Language," set in the future, in which a crowd assembles in New York to attend the messianic live performance of a formerly obscure rock musician.
Hairy at the Heel While your coworkers will naturally want to crowd around and dote on your dog, try to avoid letting too big of a crowd assemble all at once.
On Wednesday, in front of a polite crowd assembled by the Center for National Interest in Washington, DC, presidential candidate Donald Trump gave a speech ostensibly clarifying his foreign policy.
