A new poll finds that the Sept. 11, 2001, attacks are still among the most significant historical events in many Americans' lives. About half of U.S. adults consider what happened that day to be one of the most pivotal events they've lived through, 25 years later. In contrast with more recent major events, like the 2008 financial crisis, the COVID-19 pandemic and presidential elections, 9/11 stands out for its lasting impact. The vast majority of Americans remember where they were when they heard the news about the attacks, and about two-thirds say it affected the country "a great deal" or "quite a bit." However, only about 1 in 10 plan to commemorate Friday's anniversary in some way.