About 2,200 steps — the equivalent of the World Trade Center’s 110 stories — is the figure used in memorial stair climbs that honor FDNY firefighters who responded on September 11, 2001. The National Fallen Firefighters Foundation’s 9/11 Memorial Stair Climbs ask participants to climb or walk that symbolic ascent; some events cite about 2,071 steps for a 110-flight route.
No firefighter completed a full climb to the top on the day of the attacks: both towers collapsed before a rescue climb could finish. Memorial climbs use the full tower height as a tribute, while some ceremonies also mark the 78th floor, near the highest point reached by first responders such as Battalion Chief Orio Palmer in the South Tower.
Source: National Fallen Firefighters Foundation — 9/11 Memorial Stair Climbs