It took five hours to read the names of the 2,753, victims who died in New York when the Twin Towers were attacked 10 years ago.
America showed its solidarity with heartbroken family members by holding silences at 8.46am and 9.03am, marking the moment the two planes struck.
Among those remembering their loss was Robert Peraza.
His son Rob, a trader with investment bank Cantor Fitzgerald, was killed aged 30.
Touching the spot where his name is engraved at the Ground Zero memorial, he said: "Rob, we love you, we are with you all the time and we'll never forget, we'll never forget, we'll never forget."
Relatives were joined by President Barack Obama, first lady Michelle and former leader George W Bush and his wife Laura.
"God is our refuge and strength… We will not fear, even though the Earth be removed, though the mountains be carried in the midst of the sea, " said the president, reading from Psalm 46:2: