People walk near the sight of Ground Zero and the One World Trade Center on Aug. 30. The Wall Street neighborhood changed drastically after the 9/11 attacks as banks moved out of what had long been their home. Spencer Platt/Getty Images hide caption
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Left to right: Albert Petrocelli Jr., Mark Petrocelli and Albert Petrocelli Sr., on Father's Day in 1989, at Mark's home in New York. Courtesy of the Petrocelli family hide caption
Empire State Building in 1930. Lewis Hines/National Archives/Courtesy of Bloomsbury Publishing hide caption
Erika Starke, left, is comforted by her son, Michael Haub, as they attend a second funeral service for New York Fire Department firefighter Michael Haub, in Franklin Square, N.Y. The New York City medical examiner identified more of his remains recovered at ground zero. Eduardo Munoz Alvarez/AP hide caption
President Trump, first lady Melania Trump and Stephen Clark, the superintendent of the National Parks of Western Pennsylvania, walk through the Flight 93 National Memorial in Shanksville, Pa., on Tuesday. Evan Vucci/AP hide caption
WTC Cortlandt subway station reopened in New York on Saturday, nearly 17 years after it was destroyed during the terrorist attack on the World Trade Center on Sept. 11, 2001. Patrick Sison/AP hide caption
Joe Dittmar holds remnants of the World Trade Center — a section from one of the core beams of the South Tower, right, and a bolt from a steel beam. Jud Esty-Kendall/StoryCorps hide caption
Blind Sheikh Omar Abdel Rahman sits and prays inside an iron cage at the opening of a court session in Cairo in 1989. Mike Nelson/AFP/Getty Images hide caption
Omar Abdel-Rahman, Radical Cleric Connected To 1993 World Trade Center Bombing, Dies
New York City Mayor Bill de Blasio speaks to Democratic presidential nominee Hillary Clinton during a memorial service at the National September 11 Memorial and Museum. Bremdam Smialowski/AFP/Getty Images hide caption
A commemoration ceremony is held for the victims of the Sept. 11 terrorist attacks on Sunday at the National September 11 Memorial and Museum in New York City. Spencer Platt/Getty Images hide caption
Russell Mercer replaces old U.S. flags with new ones at the Flushing World Trade Center Memorial at Flushing Cemetery in New York City. His stepson, Scott Kopytko, was killed on Sept. 11. Alex Welsh for NPR hide caption
Sept. 11 Families Face 'Strange, Empty Void' Without Victims' Remains
A construction worker looks up at One World Trade Center in New York City, the central skyscraper under construction at Ground Zero, a year before its 2013 completion. Spencer Platt/Getty Images hide caption
For Those Who 'Worked The Pile' At Ground Zero, Horrors Of Sept. 11 Haven't Faded
The 9/11 Responders Remembered Memorial in Nesconset, N.Y. John Feal spends 10 hours a day vetting responders for inclusion on the memorial. Courtesy of FealGood Foundation hide caption
Honoring The Other Fallen Of Sept. 11: Sickened Ground Zero Volunteers
Then: A composite image of Donald Trump (left, clockwise), New York City Mayor Rudy Giuliani, Sen. Hillary Clinton, Tim Kaine, Rep. Nancy Pelosi and Rep. Tim Kaine. Getty Images and AP hide caption
People look out at the former site of the World Trade Center in New York City in 2005, where construction had started on Freedom Tower. Spencer Platt/Getty Images hide caption
Members of the Taliban militia ride in vehicles during Afghanistan's annual Independence Day parade in Kabul on Aug. 19, 2001. Afghanistan was largely cut off from the world during the Taliban's rule from 1996 to 2001. That changed dramatically after the Sept. 11 attacks. Saeed Khan/AFP/Getty Images hide caption
Three World Trade Center is under construction near One World Trade Center, which was completed in 2013. The new building stands 1,079 feet tall, and its topping-out ceremony was held in June. Hansi Lo Wang/NPR hide caption
In Ongoing Rebuilding Of Ground Zero, A Balance Of Remembrance, Resilience
Pope Francis places a white rose at the South Pool of the Sept. 11 memorial in downtown Manhattan on Friday. John Minchillo/AP hide caption
Relatives of victims of the Sept. 11 attacks are periodically flown down to Guantanamo Bay, Cuba, to witness court proceedings against five men accused of plotting the attacks. For the witnesses of the most recent court session, the experience raised questions about justice, humanity and the ethics of the death penalty. Joe Raedle/Getty Images hide caption
Families Of Sept. 11 Victims Watch Guantanamo Hearings With Mixed Feelings
Onlookers take cell phone pictures of stranded window washers hanging from scaffolding on the side of One World Trade Center. Timothy A. Clary/AFP/Getty Images hide caption
An artist's image of the wall that will separate the public from the repository where unidentified remains will be kept at the National September 11 Memorial Museum in Manhattan. 911memorial.org hide caption
A screen grab from an NBC New York video showing Casquejo leaving court on Thursday. NBC New York hide caption
The Willis Tower (left) in Chicago, photographed on Feb. 15. One World Trade Center (right) in New York City, photographed in November. Saul Loeb/Getty Images/Mark Lennihan/AP hide caption
One World Trade Center stands at its full height of 1,776 feet Friday, after a crane lifted its spire into place. The New York City skyline is seen here from the Heights neighborhood of Jersey City, N.J. Julio Cortez/AP hide caption