The iconic American flag three New York City firefighters raised above World Trade Center rubble on 9/11 that later disappeared has been recovered and donated to the National September 11 Memorial & Museum, 9/11 Memorial President Joe Daniels and Chubb CEO Evan Greenberg announced on the 15th anniversary of the attacks.

The historic flag went on display at the 9/11 Memorial Museum in commemoration of the 15-year anniversary of the 2001 attacks. With the help of the flag’s original owner, Shirley Dreifus, in honor of her late husband Spiros E. Kopelakis, and in cooperation with Chubb, the global insurance company, the flag was donated to the museum.

The authenticity of the flag was determined through a months-long forensic investigation.

“In the darkest hours of 9/11 when our country was at risk of losing all hope, the raising of this American flag by our first responders helped reaffirm that the nation would endure, would recover and rebuild, that we would always remember and honor all of those who lost their lives and risked their own to save others,” 9/11 Memorial President Joe Daniels said. “We had always hoped this special flag and its story would be shared with our millions of annual visitors coming from around the world, and for that, we are thankful to Shirley Dreifus, the city of Everett, HISTORY, A+E Networks, and Chubb.”

“The raising of this American flag was a powerful symbol of hope, strength and resilience at one of the most trying moments in our nation’s history,” said Greenberg. “As we prepare again to pay tribute to those who were lost, this flag is a ti mely reminder of the spirit of our heroes and the resolve of a great city and great nation. Chubb is honored to donate the flag to its new, permanent and proper home in the 9/11 Memorial Museum.”

“We are honored that HISTORY played a role in the recovery and return of the Ground Zero Flag, an important national symbol,” said Nancy Dubuc, president and CEO of A+E Networks. “The story of how the flag was found, authenticated and returned to New York is one of the great modern day mysteries solved. I am pleased we can bring the story to a wider audience through ‘Ground Zero Flag Found.'”

Since its opening in 2014, the Museum displayed a large photograph of the three firefighters lifting the flag above the rubble as part of its historical exhibition. The raising of flag was photographed by Thomas E. Franklin, formerly of The Record of Bergen County, N.J. The image, which was circulated widely, captured the fortitude of first responders and became a symbol of hope and rebuilding in the aftermath of the terrorist attacks.

The flag had been taken from the Star of America, a yacht owned by Dreifus and the late Kopelakis, which was docked at the World Financial Center. Later, a different flag was believed to be the original. But the original was actually lost and no one knew it at the time.

HISTORY chronicles the story of the flag’s recovery and journey back to New York in the special “Ground Zero Flag Found,” featuring best-selling author and HISTORY host Brad Meltzer. It premiered Sunday, Sept. 11.

The documentary follows the discovery of the flag, uncovering the mystery of its disappearance, and documenting the tests that prove its authenticity. The documentary also covers the investigation by Washington state’s Everett Police Department, whose dedication helped to bring the flag back to the public.

The story of the flag was shared in an October 2014 episode of the HISTORY series “Brad Meltzer’s Lost History,” produced by Left/Right Productions. After the episode aired, a person who wished to remain anonymous turned over the original flag to Everett police.

Police contacted HISTORY and Left/Right, and the three organizations began a forensic investigation that determined overwhelming evidence that the flag is the Ground Zero Flag. Chubb, which had insured Dreifus’s yacht, and paid a claim on the lost flag, joined her in donating to the Memorial and Museum.