Family and friends of those lost say the anniversaries never get easier. NY1's Michael Scotto got their reaction from Lower Manhattan.
For June Coppola, the heartbreak has been overwhelming. On 9/11, she lost her husband, brother, and brother-in-law.
This was the first time she could bring herself to attend a September 11th remembrance ceremony.
"I just can't believe it's been that long. It's tough to be down here again," June said. "I lived in the area. It's tough being down here."
For the family members who gathered Sunday, time has not eased the pain. Many say they come year after year because this is where their loved ones are buried.
Zoe Kousoulis's daughter Danielle was in her Cantor Fitzgerald office when the towers collapsed. Her remains were never found.
"She's buried here. They never found anything. We never got anything of her," Kousoulis said. "This is where she is, so this is where we come."
That's one of the reasons Jim McCaffrey comes as well. His firefighter brother-in-law was on the 78th floor of the South Tower when it collapsed.
He says the annual ceremony is needed not just to remember loved ones, but to ensure that the day is never forgotten.
"People need to remember what happened here, how there are people who want to destroy us, and we need to remember that," McCaffrey said. "And we need to keep that in mind so hopefully we never have another 9/11."
Throughout the morning, there were a good number of tourists lingering outside the gates, waiting for the memorial to reopen.
Louise Mensah came from England to see the World Trade Center site.
"It's haunting. There's a real sense of heartbreak just actually being here," said Louise Mensah, who is visiting the site from England. "It's important for me to see it, too."
For much of the day, the family members had the relatives to themselves, to reflect on a day that tore apart their lives.
"15 years is a long time," said Liane Nunez, who lost her aunt to the September 11th attacks.