NEVADA, Iowa (WHO) — Firefighters climbed 110 stories at the Verbio Biorefinery plant on Sunday to honor the over 300 firefighters who lost their lives at the World Trade Center in the 9/11 terrorist attacks.

Verbio North America partnered with the Nevada Fire Department to host the 4th Annual 9/11 Memorial Stair Climb. Approximately 75 participants from 20 different rescue organizations across the state climbed 110 stories, or 2,220 steps, in one of the plant towers. The climb symbolizes the effort given by the 343 firefighters killed in the attacks.

“We are grateful that we can honor those brave men and women that gave their lives to save so many others,” Nevada Fire Chief Ray Reynolds said. “The 9/11 stair climb tradition is our way to ensure their sacrifices, on one of the most tragic days in America history, are never forgotten.”

Participants had to climb the Verbio tower six times, which adds up to the height of one of the Twin Towers. During their climb, radio traffic from 9/11 was played and pictures of the firefighters who were killed were displayed on the walls.

In addition to hosting the memorial climb, Verbio presented checks to local fire departments to honor them. The Nevada Fire Department received a check of 5,000 dollars at today’s event. Fire departments in Colo, Zearing, McCallsburg, Hubbard, Rolland, and Lafayette each received checks of 2,000 dollars.