The 9/11 Tower Challenge, Glendale, AZ

Thousands of Arizonans will gather at State Farm Stadium in Glendale beginning at 7 a.m. Friday, Sept. 11, for the annual 9/11 Tower Challenge.

The event is a tribute to the first responders who lost their lives on Sept. 11, 2001, and to those who continue to serve. It will mark 25 years since the attacks.

Participants will climb 2,071 steps, the same number found in each of the Twin Towers, in remembrance of the 343 firefighters, 71 law enforcement officers and eight paramedics who died in the line of duty at the World Trade Center.