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JEFFERSON COUNTY, Colo. — More than 2,300 people from 26 states paid tribute to those who were killed in the terror attacks 17 years ago at the annual 9/11 stair climb at Red Rocks Amphitheatre on Tuesday morning.

Many firefighters and first responders chose to do the climb in full turnout gear. It’s a way to honor the 343 firefighters who were killed on Sept. 11, 2001.

Those participating will walk up and down the stairs nine times — the equivalent of climbing the 110 stories of the World Trade Center.

That attack killed nearly 3,000 people. The money raised at the climb allows the National Fallen Firefighters Foundation to support some of those families.

It’s one of about 40 climbs held across the country, but the one at Red Rocks is the largest.