The dark stone path that bisects the Flight 93 National Memorial visitors center in Shanksville, Pa., memorializes the flight path of the United Airlines plane. Gene J. Puskar/AP hide caption
Remembering Sept. 11 Remembering Sept. 11
President Obama, first lady Michelle Obama, Vice President Joe Biden and others observe a moment of silence on the South Lawn of the White House on Thursday to mark the 13th anniversary of the Sept. 11 attacks. Charles Dharapak/AP hide caption
"Timescape" finds words in the news associated with Sept. 11, and weights them according to prominence in a story — not just how often they appear. Gaurav Bradoo hide caption
Family members of victims of the Sept. 11 attacks demonstrate against the decision to transfer the unidentified remains to a repository at the World Trade Center site. Eric Thayer /Reuters /Landov hide caption
A woman looks out at One World Trade Center from inside the 9/11 Empty Sky memorial at Liberty State Park in Jersey City, N.J., on Wednesday. Americans commemorated the 12th anniversary of the Sept. 11 attacks with solemn ceremonies and pledges to not forget the nearly 3,000 people killed. Gary Hershorn/Reuters/Landov hide caption
Robert Peraza, who lost his son Robert David Peraza, pauses at his son's name at the North Pool of the 9/11 Memorial at the site of the World Trade Center. Justin Lane/pool/Getty Images hide caption
Singer Patti LaBelle performs during the "Concert For Hope" event, hosted by Washington National Cathedral, to mark the tenth anniversary of the 9/11 terrorist attacks. Alex Wong/Getty Images hide caption
Alan Jackson
U.S. soldiers pray during the an anniversary ceremony of the terrorist attacks on September 11, 2001 at Bagram Air Field, Afghanistan. John Moore/Getty Images hide caption
Keri McMorrow, 7, visits the memorial pool where her uncle's name is engraved, during tenth anniversary ceremonies of the September 11, 2001 terrorist attacks at the World Trade Center site. Pool/Getty Images hide caption
Kids and Sept. 11: The Day 'Children Realized ... Grownups Were Vulnerable'
Family members of the victims entered the 9/11 Memorial Plaza for the first time today. Chip Somodevilla/Getty Images hide caption
Paul Simon singing 'The Sound of Silence'
From New Jersey early today, the view across the Hudson River to the World Trade Center. Joel Rose/NPR hide caption