The Never Forget Walk is a 500 mile journey to NYC

In just over a month, New York and the nation will pause to mark the 20th anniversary of the 9/11 terrorist attacks.

Tunnel to Towers CEO Frank Siller just kicked off a five-hundred-mile walk from Washington D.C., which will culminate on September 11th at Ground Zero in remembrance of the 2,977 lives lost that day.

"I mean, they knew the possibility when they were going into those towers that they were going to die," he says about the heroic first responders who ran into the burning buildings.

Siller began his journey by laying a wreath just feet away from where American Airlines Flight 77 struck the Pentagon.

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The 68-year-old will travel on foot, first, to Shanksville, Pennsylvania, home to the Flight 93 national memorial.

Then, he’ll continue through the Battery Tunnel to the site where the World Trade Center once stood.

It's the very same path his brother and off-duty firefighter, Stephen, took two decades ago, sacrificing his own life to save others in the name of freedom.

"I think of all 343 firefighters off duty that day and some of them were on duty," he adds.

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Twenty years later, Siller's memory lives on through the Tunnel to Towers Foundation.

The non-profit builds mortgage-free smart homes for injured veterans and first responders, and also for the families of heroes who are killed in the line of duty.

Behind every step is a sacrifice that will never be forgotten.