Of all the photographs that documented the horror of September 11th, one of the most enduring is the image of three firefighters raising an American flag in the rubble of the World Trade Center. The photo, called Raising the Flag at Ground Zero, snapped by the Bergen Record's Thomas E. Franklin, won a slew of awards and was turned into a stamp. The flag was unfurled at Yankee Stadium, signed by Rudy Giuliani and George Pataki and sailed around the world with the Navy. But by 2002, people realized that the flag making the rounds wasn't the correct one, starting a years-long hunt for the original flag.

The flag, finally located, will be returning home to the September 11th Memorial and Museum with an unveiling tomorrow.

The flag came from Star of America, a yacht docked near Ground Zero. As it turns out, the flag went missing just hours after the iconic picture of firefighters raising it was snapped, though no one on the scene appears to have been aware of that fact. But it wasn't until the summer of 2002, when the flag was supposedly returned to the owners of the Spirit of the America, that anyone realized that this flag was not the original. The flag given to the yacht's owners was five feet by eight feet, but the flag on the yacht was three feet by five feet. The hunt for the real flag was on. And went nowhere for over a decade.

Finally, the search caught a break during the premiere episode of Brad Meltzer's Lost History in 2014. A few days after the episode aired, a man calling himself "Brian" dropped what he said was the Ground Zero Flag off at a fire department in Everett Washington. The Everett Herald has the long, two year story of how the flag was kept a secret by the Everett police while they had forensics experts test it for authenticity.

The flag was tested for debris from Ground Zero, which it had, but DNA found on it didn't match up with any of the firefighters photographed raising it. The History Channel flew out a woman who worked on the Star of the America, who said she was "80 percent sure" that flag in Everett was the flag. Pictures of the flag were pored over to look for the smallest similarities between it and the Everett flag. Finally, after two years, it was determined the Everett police had enough evidence to prove the flag they had was the one from the Star of the America.

The last remaining mystery of the flag is how "Brian" wound up with it. He told Everett firefighters that he was a former Marine and had been given the flag by an employee of the National Oceanic and Atmospheric Administration, who had gotten it from the widow of a 9/11 victim. But since the flag still had some of its equipment and rope attached to it, John Cutter, formerly of the NYPD's criminal intelligence division, told the History Channel he doubted the flag originally came from a 9/11 widow.

Whoever Brian is and however he wound up with the Ground Zero flag, it's coming back home now. The flag was donated to the 9/11 Museum by the surviving owner of the Spirit of the America, Shirley Dreifus, and will be unveiled on Thursday morning at a ceremony there.