Like many events, the race was not held last year due to the coronavirus pandemic.
This year, roughly 30,000 people took take part.
First-time participant Patrick Kelly said he was paying tribute to his friend, FDNY firefighter Michael Cawley of Ladder 136.
"Michael was off that morning, finished his shift and stayed around, like many people, like Stephen Siller and ran into that building and gave his life," Kelly said.
Others like volunteer firefighter Robert McIntyre of the Plandome Fire Department, says he would have done the same "in a heartbeat."
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"If other people in my neighborhood were able to run though my home to help me, I should be able to help them," he said.
The event traces Siller's final heroic steps before he died during the September 11 terror attacks.
Participants started at the Hugh Carey Tunnel in Brooklyn and ran or walked to the former site of the original World Trade Center complex.
The route honors the moment Siller abandoned his truck in Brooklyn and ran through the tunnel towards the towers after they were attacked.
Proceeds from the event benefit the Stephen Siller Tunnel to Towers Foundation, supporting first responders and wounded veterans of the Iraq and Afghanistan wars.
Siller's brother Frank, set up the foundation, which has spent more than $250 million helping those affected by 9/11.
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