Maybe the concern wasn't rational. How could anyone forget Sept. 11?
But among those who lost loved ones in the terrorist attacks, worries emerged: What happens when details of that day fade? What if everyone else forgets?
And so memorials appeared — on bookshelves and street corners, in gardens and on people's flesh. They are elaborate and simple, public and private, universal and individual. They're made up of pictures, poems, pieces of the wreckage.
Richard Pecorella got a street named after the love of his life, Karen Juday. He has a bookcase full of pictures and mementos in his office. And he keeps searching for her among pictures of the jumpers.
"If she jumped, as far as I'm concerned, she didn't suffer," he says.
Lynda Fiori decided a week after she lost her husband Paul to get a tattoo in his memory. Her brother joined her. Soon, others in the family did the same. "In Memory of Paul," some tattoos say, along with the infamous date.
"I don't ever want him to be forgotten," Lynda Fiori says. "But I can't stand remembering it."
In some memorials, it's hard to miss ironies.
In one, a statue of Jesus Christ holds the twin towers, even though that day felt so unprotected, so diabolical.
The firefighters and police officers look strong and fearless in their pictures, even though they could not defeat the fire, steel and gravity.
The items that Regina Coyle displays in a glass case memorialize her firefighter son James Coyle, and yet they taunt her.
"It's funny looking at all the medals over here, it's ironic cause my son wasn't trying to be a hero, he was just trying to do his job," she says. "And to look here and to see that's all you have left of him — that's not James."
In a Staten Island traffic circle, pictures of victims are lined up in rings along with statues of angels. It is called Angels Circle. For many families who never received remains to bury, it is like a cemetery.
"Groups of people will come and sit down — it's very peaceful," said Wendy Pellegrino, the site founder. "They'll celebrate their birthdays or an anniversary or whatever. It's just turned into a very comforting place for them."