Ground Zero: September 11, 2001 - September 11, 2011

One of the most indelible memories in the collective psyche of Americans - and the world - comes from the images of the World Trade Center following the terrorist attacks on the United States, September 11, 2001. Yesterday, Americans and the world collectively remembered those who lost their lives in New York, Washington and Pennsylvania ten years after that unforgettable day. This post (edited by Leanne Burden) shows the transformation, of what became known as Ground Zero, over the last ten years. A memorial rises from the ashes of that day on September 11, 2011. -- Paula Nelson (41 photos total)

Photos by Space Imaging’s IKONOS satellite showing the World Trade Center complex in Manhattan, New York, collected on June 30, 2011 showing the 110-stories twin towers; on September 15, 2001 showing the remains of the 1,350-foot (411.48-meter) twin towers of the World Trade Center, and the debris and dust that have settled in Ground Zero, four days after the terrorist attacks; and June 8, 2002, showing the progress in the reclamation of Ground Zero where the twin towers of the World Trade Center once stood. AFP/Space Imaging

A man stood in the rubble and called out, asking if anyone needed help, after the collapse of the first World Trade Center Tower on Sept. 11, 2001. More than 2,700 people were killed when Al Qaeda terrorists hijacked US passenger jets and flew them into the twin towers in New York. Doug Kanter/AFP

An aerial view of the wreckage at the World Trade Center on Sept. 16, 2001. New York City Office of Emergency Management

Workers climbed over the remains of the World Trade Center complex in lower Manhattan, New York, on Sept. 28, 2001. Shawn Baldwin/Associated Press

Firefighters made their way over the ruins of the World Trade Center through clouds of smoke as work continued at ground zero on Oct. 11, 2001, one month after the terrorist attacks. Stan Honda/Associated Press

Sunlight filtered into the still smoldering remains of Tower Two as workers riding in a basket suspended from a giant crane hovered above on Oct. 27, 2001. William C. Lopez/Associated Press

A major section of Building 6 collapsed as demolition of the remaining piees of the World Trade Center continued on Dec. 18, 2001. Louis Lanzano/Associated Press

Recovery workers looked on as heavy machinery helped remove debris on Jan. 12, 2002. Robert Spencer/Associated Press

Workers unfolded an American flag on May, 25, 2002, on top of the last standing beam at the site of the World Trade Center disaster in New York a few days before the official end of the recovery effort. Stephen Chernin/Associated Press

The former site of the World Trade Center, known as ground zero, was seen from the southeast in this photo taken on June 4, 2002. Peter Morgan/Reuters

At ground zero, a lone police officer sat amid the rubble during a ceremony marking the one year anniversary of the attacks on Sept. 11, 2002. Amy Sancetta/Associated Press

Lights illuminated ground zero as the sun set over the Manhattan on Sept. 6, 2002. Vincent LaForet/The New York Times

The original slurry wall of the World Trade Center, showing steel old cement and the new resh cement, was visible on Nov. 19, 2003. Angel Franco/The New York Times

Workers laid the cornerstone of the Freedom Tower on the location of the World Trade Center on July 4, 2004. James Estrin/The New York Times

People looked out at the former site of the World Trade Center on May 5, 2005. The construction of the Freedom Tower on the site had run into numerous obstacles. Spencer Platt/Getty Images

On the east side of the World Trade Center bathtub, the old inbound Hudson & Manhattan Railroad tunnels, which also served as truck ramps for the World Trade Center, were visible on July 16, 2005. Andrea Mohin/The New York Times

A worker dismantled the T-shaped steel beam, which gained fame as the ground zero cross, on Oct. 5, 2006. The cross was found by a construction worker amid smoking ruins two weeks after the Sept. 11 attacks. Bebeto Matthews/Associated Press

Construction workers watched from a ramp as others raised the first of three 25-ton steel columns into position before it was bolted into place on Dec. 19, 2006, a milestone in efforts to build a new office tower to replace the World Trade Center. Kathy Willens/Associated Press

Construction at the foundation of the Freedom Towers at the World Trade Center site in New York, September 10, 2007. Shannon Stapleton/Associated Press

Construction continued on the Freedom Tower foundations at the World Trade Center site on June 20, 2008. Mark Lennihan/Associated Press

The galleria at the World Trade Center, an east-west underground connecting passageway between the Transportation Hub and Battery Park City, was still exposed to daylight during construction on Nov. 18, 2008. David W. Dunlap/The New York Times

Friends and relatives of the victims of the Sept. 11 attacks tossed flowers into the Reflecting Pool during a ceremony at ground zero on Sept. 11, 2008. Andrew Harrer/Bloomberg News

The survivors’ staircase at the World Trade Center was moved to its permanent spot on Dec. 11, 2008. The Vessey Street staircase was used by many to evacuate the towers on Sept. 11, 2001. Ozier Muhammad/The New York Times

The sunken pool, which marks the site of One World Trade Center, was almost entirely framed out in structural steel, except for its southwest corner in a January 2009 photo. Port Authority of New York and New Jersey

Ironworker Eon Mathieson prepared to connect a steel beam on the fourth floor of One World Trade Center on Nov. 17, 2009. The Port Authority changed the name from Freedom Tower to One World Trade Center in 2009. Mark Lennihan/Associated Press

People watched out the window as construction continued at the World Trade Center site on March 26, 2010, in New York City. A new development agreement was announced after a 16-month stalemate over building at the site. Mario Tama/Getty Images

A 19th-century ship that has been buried for over 100 years was found on July 14, 2010, during construction at the former World Trade Center site. Archeologists worked to uncover, measure, and collect artifacts quickly before the ship would be buried again. Fred R. Conrad/The New York Times

Work in the memorial pools continued on Aug. 27, 2010. Fred R. Conrad/The New York Times

Looking up at the base of one of the cranes at the One World Trade Center on Aug, 27 , 2010. Fred R. Conrad/The New York Times

Construction continued at the World Trade Center site with the memorial footprints of the twin towers visible on Sept. 7, 2010. Mario Tama/Getty Images

A trumpeter played Taps at ground zero at the end of the ninth annual commemoration ceremony on Sept. 11, 2010. Chris Hondros/Getty Images

People stood on the 20th floor restaurant terrace of the World Center Hotel as construction continued on One World Trade Center and the National September 11 Memorial & Museum on July 8, 2011. The memorial features two reflecting pools on the footprints of the twin towers. Mario Tama/Getty Images

Clouds were reflected in the glass of One World Trade Center on May 11, 2011. The base of the tower was supposed to be covered by prismatic glass panels to cover the bomb-proof concrete, but plans were scrapped. Todd Heisler/The New York Times

Tourists looked on as the Fire Department of New York's Ladder Company 3 fire truck, which was responsible for evacuating civilians from the North Tower of the World Trade Center on Sept. 11, 2001, was lowered 70 feet by crane to its exhibition space of the National September 11 Memorial Museum on July 20, 2011. Timothy A. Clary/AFP/Getty Images

Construction workers lowered the Sept. 11 cross by crane into a subterranean section of the National September 11 Memorial and Museum on July 23, 2011. The cross is an intersecting steel beam discovered in the World Trade Center rubble which served as symbol of spiritual recovery in the aftermath of 9/11. Mark Lennihan/Associated Press

Two steel beams known as the tridents from the original World Trade Center tower were visible inside the National September 11 Museum during construction on July 28, 2011. Mike Segar/Reuters

A flag flies over Ground Zero before the start of ceremonies marking the 10th anniversary of the 9/11 attacks on the World Trade Center, September 11, 2011. Gary Hershorn/Reuters

The World Trade Center ceremony marking the 10th anniversary of the attacks takes place at the National September 11 Memorial, Sept. 11, 2011 in New York. Mark Lennihan/Associated Press

A flag flies over ground zero before the start of the ceremony marking the 10th anniversary of the 9/11 attacks. Eduardo Munoz/Reuters

A framed photo of the Twin Towers sits against a curb in honor of a 9/11 victim near Ground Zero during the 10th anniversary ceremony, September 11, 2011, in New York. Tom Fox/The Dallas Morning News