President Trump led a national moment of silence on the 16th anniversary of the terrorist attacks on the World Trade Center and the Pentagon on Monday, the first commemoration for a New York native who has described the destruction of the Twin Towers as a defining event in his political life.

At the White House, Mr. Trump and Melania Trump, the first lady, marked the moment, 8:46 a.m., when the first airliner struck one of the towers, leading to a catastrophic collapse that killed nearly 3,000 people, 343 of them New York City firefighters.

The first couple walked out of the White House at 8:45 a.m. A minute later, a bell tolled as they stood near a group of White House staffers and invited guests who bowed their heads as a Marine trumpeter played taps. The president and first lady placed their hands over their hearts and walked silently back into the residence at 8:48 a.m.