A detail of a World Trade Center 'trident', a steel column that formed part of the building's structural support, seen during a press preview in the National September 11 Memorial Museum at the World Trade Center site May 14, 2014 in New York.
Escalators going up to street level past a section of steel facade from the North Tower, floors 96 to 99, (L) seen during a press preview in the National September 11 Memorial Museum at the World Trade Center site May 14, 2014 in New York.
The bullhorn President George W. Bush used to speak to first responders and the public at Ground Zero on September 14 is viewed during a tour the National September 11 Memorial Museum on May 14, 2014 in New York City.
A display of 'missing people' posters that were hung around New York City after the September 11, 2001 attacks on the World Trade Center, seen during a press preview in the National September 11 Memorial Museum at the World Trade Center site May 14, 2014 in New York.
Surviving firefighter Dan Potter's fire helmet, which he used at Ground Zero on September 11, is viewed during a tour the National September 11 Memorial Museum on May 14, 2014 in New York City.
Cards, patches and mementos of those killed at Ground Zero are are viewed during a preview of the National September 11 Memorial Museum on May 14, 2014 in New York City.
A pair of eye glasses recovered from Ground Zero are viewed during a preview of the National September 11 Memorial Museum on May 14, 2014 in New York City.
Detail of objects found after the September 11, 2001 attack on the Pentagon, seen during a press preview of the National September 11 Memorial Museum at the World Trade Center site May 14, 2014 in New York.
Pieces of the plane of Flight 11 seen during a press preview of the National September 11 Memorial Museum at the World Trade Center site May 14, 2014 in New York.
A firefighters shirt used at Ground Zero on September 11 is viewed during a tour the National September 11 Memorial Museum on May 14, 2014 in New York City.
A photograph of one of the World Trade Center towers collapsing after the September 11, 2001 attack, seen during a press preview of the National September 11 Memorial Museum at the World Trade Center site May 14, 2014 in New York.
A New York Fire Department ambulance, is seen during a press preview of the National September 11 Memorial Museum at the World Trade Center site May 14, 2014 in New York.
Artifacts from Ground Zero, including part of a television and radio antenna from the North Tower, is viewed during a preview of the National September 11 Memorial Museum on May 14, 2014 in New York City.
A quote from Virgil seen during a press preview of the National September 11 Memorial Museum at the World Trade Center site May 14, 2014 in New York.
An American Flag recovered from the World Trade Center site is viewed during a preview of the National September 11 Memorial Museum on May 14, 2014 in New York City.
The symbolic Last Column (R), a steel beam from one of the World Trade Center towers, stands near the Slurry Wall (L), which holds back the Hudson River waters, seen during a press preview of the National September 11 Memorial Museum at the World Trade Center site May 14, 2014 in New York.
The salvaged tridents from the World Trade Center are viewed during a preview of the National September 11 Memorial Museum on May 14, 2014 in New York City.
A destroyed fire department ambulance from Ground Zero is viewed during a preview of the National September 11 Memorial Museum on May 14, 2014 in New York City.
Artifacts from Ground Zero is viewed during a preview of the National September 11 Memorial Museum on May 14, 2014 in New York City.
Dust, ash and debris from the collapsed Twin Towers are viewed on the clothes from the store Chelsea Jeans in an exhibit at viewed during a preview of the National September 11 Memorial Museum on May 14, 2014 in New York City.
The 'Survior Stairs', remnants of a Vesey Street staircase where many people who worked at the World Trade Center towers during the September 11, 2001 attack escaped to the street, seen during a press preview of the National September 11 Memorial Museum at the World Trade Center site May 14, 2014 in New York.