As the United States marks the 20th anniversary of the attacks on September 11, 2001, it also provides a reminder that the events happened a while ago. American society and the world were different then. Here are a few scattered thoughts on how this passage of time influences how Americans view that day.

-I saw a statistic that roughly 1/4 of Americans alive today were not alive on September 11, 2001. I have been aware of this for at least a few years as the college students I teach were either very young or not yet alive then. To a significant number of Americans, 9/11 is history.

-So much has happened since then that makes it all seem like a different era. The response to the attacks kicked off the War on Terror and the consequences are still being felt (see recent events in Afghanistan). Political polarization increased. The housing bubble burst and more economic instability seems present. Two presidents served their time in office and did so in very different ways.

-The commemorations often stress the quick coming together for rescue and cleanup efforts alongside the expressions of unity among members of Congress and Americans. This did not last long.

-We now have official memorials in numerous locations, including at the sites of the attacks and in communities around the country. Will these be altered or viewed differently as years go by?

Future commemorations will face these issues even more. The United States is not new to such change – how D-Day and Pearl Harbor are marked differs with the increasing age of those alive at the time and World War II might seem like eons ago, the memory of the Civil War has been a conflict for over a century – but subsequent decisions and events could solidify or change 9/11 narratives in ways that might be hard to predict.