343 firefighters climbed up 110-stories on September 11, 2001 as response to the terror attacks on the World Trade Center. The collapse of the skyscraper killed all of them.
12 years later, fire fighters from across the country held events on Wednesday to do the same in climbing 110 flights of stairs, some carrying the full 60-pound firefighting gear.
Meanwhile, 343 flags were placed at the Firefighter's Monument to honor the FDNY members killed on 9/11.
The 343 firefighters who lost their lives on 9/11 have also been honored around the country in public memorials, silent prayers, and internet messages.
On Twitter, the terms "Never Forget" and "Remember 911″ have been trending.