Twenty years ago this week, on a morning when the air was remarkably clean and fresh and the sky was a gorgeous blue, I was feeding my then-19-month-old daughter in her high chair by a window in our home in Brooklyn when I heard a loud crashing sound and saw a huge flock of pigeons scramble chaotically into the sky. I soon saw what the rest of the world would quickly learn that day—that two planes had deliberately flown into the World Trade Center. Another plane, I learned after turning on the news, had flown into the Pentagon and one, headed for Washington, D.C., had crashed in Pennsylvania after the brave souls on the plane attempted to thwart the hijackers plans. As my husband, a reporter at a major New York metropolitan newspaper, raced out the door heading toward lower Manhattan just across the river, I watched on TV as the towers fell. Needing to get out of the house and away from the disaster, I took my daughter to a nearby park, and as we walked I saw the billowing smoke headed to Brooklyn. And then it began to snow: Ash and charred documents fell from the sky, landing on the stroller and the ground around us.

That was the day New York changed—when the U.S. and the world changed. Thousands of lives were lost, and most New Yorkers who lived here then have a story—and many know someone who died that day. It is also the day that triggered the 20-year war in Afghanistan that just ended.