The unfinished One World Trade Center, the flagship of the redeveloped site, is seen behind a U.S. flag on September 7, 2012. The tower, due to be completed in 2014, will rise to 1,776 feet.
The World Trade Center site as it appeared 11 years ago. One week after the attacks, firefighters and search and rescue workers were battling smoldering fires as they searched for victims.
By 2006, the former World Trade Center site had been transformed into an enormous construction site.
With the redevelopment well under way, lower Manhattan is bustling once again. Here, people walk past the One World Trade Center tower on August 8, 2012.
One World Trade Center is seen from the 72nd floor of a neighboring tower, Four World Trade Center. The reconstruction project at the site of the attacks has a projected price tag of $14.8 billion.
Construction workers work on the 72nd floor at Four World Trade Center on September 7, 2012.
One World Trade Center stands tall on the skyline as a man takes a picture from in Hoboken, New Jersey, on September 9, 2012.
Ava Kathleen Schmoelzer, age 7, places flowers by the memorial pool at the World Trade Center site in memory of her aunt during commemorations on the eleventh anniversary of the attacks.
A day before the anniversary, a memorial light display, called The Tribute In Light, illuminates the night sky in New York.