ROCKFORD – An annual physical challenge to honor first responders and pay tribute to those who sacrificed their lives on Sept. 11, 2001, returns this Sunday. Hero Climb challenges participants to climb 110 flights of stairs in a symbolic gesture to commemorate the 343 New York City firefighters who died responding to the terrorist attacks on the Twin Towers. The attack, which was the deadliest in U.S. history, killed nearly 3,000 people.