Now, ten years on, just 12 of these heroic canines survive, and they have been commemorated in a touching series of portraits entitled 'Retrieved'.
The dogs worked tirelessly to search for anyone trapped alive in the rubble, along with countless emergency service workers and members of the public.
Traveling across nine states in the U.S. from Texas to Maryland, Dutch photographer Charlotte Dumas, 34, captured the remaining dogs in their twilight years in their homes where they still live with their handlers, a full decade on from 9/11.
Their stories have now been compiled in a book, called Retrieved, which is published on Friday, the tenth anniversary of the attacks.
Noted for her touching portraits of animals, especially dogs, Charlotte wanted 'Retrieved' to mark not only the anniversary of the September 2001 attacks, but also as recognition for some of the first responders and their dogs.
There are links at the bottom of this page to this book and another fabulous book, Dog Heroes of September 11th: A Tribute to America's Search and Rescue Dogs
'I felt this was a turning point, especially for the dogs, who although are not forgotten, are not as prominent as the human stories involved,' explained Charlotte, who splits her time between New York and Amsterdam.
'They speak to us as a different species and animals are greatly important for our sense of empathy and to put things into perspective.'