Mourners gathered in Lower Manhattan and across New York City on Wednesday to commemorate the nearly 3,000 people who died in the Sept. 11 attacks 23 years ago and the many who have died from related illnesses since.

Brandon Remouns, 40, was among those who headed to the World Trade Center memorial for the annual commemoration of the attacks. He said his father, George Remouns, was a detective who responded to ground zero on Sept. 11. He died in 2017 of cancer caused by his rescue work.

The most meaningful part of the ceremony was hearing the names of those killed read aloud, Mr. Remouns said.

“You pay your respects,” he said, adding: “It’s a long day.”

Each passing anniversary gets more difficult, said Terry Sholty Strada, whose husband, Tom Strada, worked at Cantor Fitzgerald, one of the companies with offices in the World Trade Center that lost hundreds of employees on Sept. 11. Her husband died that day, Ms. Strada said, and she was “coming to pay respects for his murder.” Their children were 7, 4 and 4 days old at the time.

“They’re all adults now, doing their own thing and just starting the cycle of life,” said Ms. Strada, 62. “And it just starts to kind of get harder again, because they’re off doing their thing and he’s not here for any of it.”

The families were joined at ground zero by President Biden and a number of other politicians, including Vice President Kamala Harris and former President Donald J. Trump, who were in New York City after facing off in their first presidential debate in Philadelphia on Tuesday evening.