For some it's history
Do you remember where you were on September 11, 2001? I was at home, watching the news, I stepped away to help my young daughter and when I came back, the South Tower was gone.
A few years ago, my son's fifth grade class read Towers Falling by Jewell Parker Rhodes. I read along with him, and it was one of the first times that I understood that to my children, and so many others, September 11, 2001 was not a powerful memory or a deep wound, but a historical event.