At the annual Tunnel to Towers 5K, participants walk or run to retrace the footsteps of FDNY firefighter Stephen Siller.

On Sept. 11, 2001, Siller strapped on his full gear and ran through the Hugh L. Carey tunnel, formerly Brooklyn-Battery Tunnel, from Brooklyn to the World Trade Center and died saving others.

“Now you get to actually walk the footsteps of this man, this legend,” participant JoAnn Stach said.

“It’s a way of showing our families that we’re never going to forget the sacrifice that their loved ones made, and that they continue to make every year,” Sal Cassano, former FDNY commissioner and executive board member of the Tunnel to Towers Foundation, said.

Cassano has been taking part since the event began in 2002 with around 1,500 people. It has grown in size over the years, attracting thousands of participants, including first responders, their families, cadets, veterans and service members, according to organizers.

“Coming out of the tunnel is so moving, with all the people standing there with all the pictures of people who’ve passed, and the servicemen and women and our first responders who gave up their lives for us that day, so it’s important to honor them,” 28-year-old Erin Walther, who first participated when she was a child, said.

The event is also a chance to honor those who continue to die from 9/11-related illnesses and others who have lost their life in the line of duty.

“My husband was Lt. Joseph Stach Jr., of FDNY. He passed away six years ago from 9/11-related cancer,” Stach said. This is her third year running.

Others taking part say they feel a sense of community on this day.

“I keep coming back because it’s for a great cause. The foundation is wonderful, and I have family members who were affected by this event [9/11] as well, so it’s nice to give back for that,” Walther said.

“When you’re the recipient of assistance from Tunnel to Towers, you become part of the Tunnel to Towers family immediately. It’s contagious that their message of ‘do good’ becomes your mantra,” William McNamara, a former police officer injured in the line of duty and now in a wheelchair, said.

Participants said the rainy weather didn’t stop them.

“It’s motivating, and believe it or not, we do wanna slow down [our pace], and every step of the way, everyone is tapping your back like, let’s go, let’s go, let’s go, and you can’t even help it. You have to just keep going,” Ruben Pires, a firefighter from New Jersey who completed the 5K in his own gear, said.

The Tunnel to Towers Foundation says their mission is to provide mortgage-free homes to Gold Star and fallen first responder families with young children, and to build smart homes for injured veterans and first responders.