In Focus delivers deeper coverage of the political, cultural, and ideological issues shaping America. Published daily by senior writers and experts, these in-depth pieces go beyond the headlines to give readers the full picture. You can find our full list of In Focus pieces here.

“History,” the American writer William Faulkner famously observed, “is not was, it is.” Sept. 11 is that rare thing in history: an undeniable hinge point in which one era ended and another, more uncertain one began. Yet, for all of its well-deserved infamy, one of the worst and most consequential days in U.S. history also remains one of the most misunderstood.