Last year’s 10th anniversary of the Sept. 11, 2001, attacks on the United States by al-Qaida terrorists attracted an extra measure of attention, as was to be expected. But remembering that awful day, that day of eternal infamy, and honoring the roughly 3,000 victims of attacks in New York City, Washington and Pennsylvania, is something the citizens of America must do on every anniversary, whether it ends in a zero or not. We owe the victims and their families that much. To not let that memory fade. Ever.

Today, there will be memorials in Washington and New York, and yes, there’s a monument in southwestern Pennsylvania to the passengers of a flight bound for the U.S. Capitol but thwarted by those on board who fought with the hijackers to take it down. At all these places, words will be spoken and wreaths arranged and families of victims honored along with the victims themselves.

And though this is not an anniversary ending in a round number, it has a powerful ability to stir clear memories of that day, the blue skies in the nation’s greatest city, the charred hole in the Pentagon, the wreckage in that field. And we remember as well the killing in the early morning of May 2, 2011, of the attack’s mastermind, Osama bin Laden, who might have wished martyrdom but instead is held by most as a symbol of evil and hate.

He is gone, along with most of his lieutenants, although there remain pockets of al-Qaida in the world, and the Taliban Islamic fundamentalist group is trying to regain absolute control in Afghanistan against an embattled government supported by the United States – whose combat role in that country is winding down.

Americans who had little knowledge of radical Islamic terrorism or its leaders before 9/11 now have a full vocabulary of names and terms. They are more familiar with the violence that Taliban leaders and their troops commit against their fellow citizens, especially women, who are singled out for incredible oppression and physical abuse.

All because of 9/11, people once unknown are known. Because of 9/11, we are aware that terrorism is likely to be a sustained threat, even without the backing of bin Laden’s inherited fortune and the leadership of bin Laden himself.

After Sept. 11, 2001, everything changed. Air travel in the United States and elsewhere became more onerous because of intensified security checks. Border crossings, likewise.

This is the anniversary of a day about which we’ll remember details. This day in the Triangle, for example, is supposed to be much the same as it was in 2001, sunny and bright and very typical of late summer. The same is true of New York City, where it will be in the mid-70s and clear. In lower Manhattan where the World Trade Center towers used to stand, thousands will remember the towers, framed by a blue sky that day, as people were going to work a little before 9 a.m.

And they’ll recall in detail the sight of those two airliners, crashing one by one into the twin towers. First there was disbelief, then terror, then anguish as the dust started to dull that bright sky. Then came the months of aftermath, searching the site for remains. The memories linger of President George W. Bush standing with a fireman atop the rubble, of then-Mayor Rudy Giuliani walking the streets with his protective mask.

Yes, eleven years later the memories are clear. They should be. They must remain forever so.