Among various tributes marking the 12th anniversary of the September 11 terrorist attacks, many of the most moving have contained images—the professional and ameteur photographs that haunted photo editors, time-lapse footage of the 9/11 Memorial being built at Ground Zero, and, of course, the images, seen firsthand and on television screens across the world, seared into our memories from that day. There is another iconic image from the immediate days afterward: Art Spiegelman’s Sept. 24, 2011 New Yorker cover, featuring the outline of the two towers against a black background.Today in the Atlantic, Jeet Herr reveals the little-known story behind the image, which is actually a collaboration between Spiegelman and his wife Françoise Mouly, the New Yorker’s art editor. (As recently as 2011, Mouly gave Spiegelman full credit for the cover.)Spiegelman and Mouly, who lived in SoHo, saw the first plane crash into the North Tower and rushed to get their two young children home safely from school. Once the nuclear family was safe and accounted for, Spiegelman began to deal with the devastation the only way he knew how: drawing.Spiegelman, then a staff artist for the magazine with many covers under his belt, went to work in his studio, a few blocks from their loft. The next day, Mouly found a friend to stay with the kids and went into the New Yorker’s midtown office to face the impossible task of coming up with an appropriate cover. She remembers thinking, “I want no image. I can’t do this. No image can do justice to this.” Mouly explained her dilemma to a neighbor, a fellow mother, who responded by saying, “What, you have to go to work to do a magazine cover? That’s ridiculous! I’ll tell you what you do: no cover.”While Spiegelman drew a cover with “the towers covered in a Christo-like black shroud against a Magritte-style blue sky,” Mouly was inspired by her neighbor to use negative space. They decided to combine their ideas, settling on a darkened silhouette of the Twin Towers set on a black background. Mouly drew it up, and the rest, as they say, is history. Or at least it is now.