Watch: 9/11 Commemoration Ceremony Honors Victims 21 Years Later

NEW YORK CITY — New York City cannot, and will not, forget.

Families of those who died during terrorist attacks on the World Trade Center will gather Sunday at Memorial Plaza to read the names of 2,977 people killed on Sept. 11 and the six who died in the 1993 bombing.

There will be six moments of silence to mark the darkest moments of the day: when planes hit the towers, when the towers fell, when a plan hit the Pentagon, and when United Airlines Flight 93 crashed in Pennsylvania.

The 9/11 Memorial and Museum is also asking New Yorkers to take photos of the sky and post them to Instagram with hashtag #NeverForget911 and #RememberTheSky.

President Joe Biden, who attended last year's ceremony in New York City, will attend a ceremony Sunday at the Pentagon.

New Yorkers are invited to view a live stream of the ceremony that will begin Sunday, Sept. 11, at 8:40 a.m.

In downtown Manhattan, the following streets will be closed.

• Areas bounded by Barclay Street on the North; Rector Street on the South; Broadway on the East; West Street on the West (All Inclusive)
• Liberty Street between West Street and South End Avenue
• Albany Street between West Street and South End Avenue
• West Thames Street between West Street and South End Avenue
• South End Avenue between Liberty Street and West Thames Street
• Battery Place between West Thames Street and 3rd Place
• 3rd Place between Battery Place and Little West Street
• Little West Street between 3rd Place and Battery Place

The memorial arrives on the heels of a loss in downtown Manhattan — last month "financial hardships forced New York City's 9/11 Tribute Museum to close.

"As someone ... there that day I know how important it is," said one petitioner who hoped to save the museum. "Never forget can't just be words."