But why hasn’t something that only lasted as a four-year insurgency against the life of the American nation just gone away? Why are its symbols, especially flags, still so controversial?

Landrieu pointed in several ways to the answer. Everyone has his or her own “journey on race,” he remarked. Imagine an American nation without slavery and race and there would have been no Confederacy, no insurgency, no flags, no Lost Cause, no R. E. Lee, no massive monuments of generals, farm boys, and politicians musing down and out at us all over the land. The Confederacy will and should remain an enduring subject of study and teaching. Just how reverentially it should be treated, and where in our public memory it ought reside, are the questions.

Landrieu is right to associate Lee and the other major statues of New Orleans with the Lost Cause tradition. Those tall memorials adorning so many Southern cities, often equestrians, were not only honors to individual men and heroes. They were erected, as Landrieu said, “to rewrite history to hide the truth, which is that the Confederacy was on the wrong side of humanity.” One might wish that the word “truth” would not be so easily thrown around, slipping in and out of everyone’s grasp. But Landrieu is right; the monuments now removed were there to “purposely send a strong message to all who walked in their shadows about who was still in charge in this city.”

Different constituencies have had wildly opposite reactions to that Lee statue over the years; Landrieu offered a bold hope of squaring those opposites. There are no utopias in the politics of historical memory. Each person holds a treasury in his or her mind when it comes to the past, and historians are far outnumbered by public memory. But we are a learning species, despite how we behave. Eloquence alone cannot solve these dilemmas, but Landrieu at least made a start.

It is difficult for historians to favor monument destruction or removal. We worry endlessly about historical erasure or purposeful ignorance of any kind. We favor debate however conflicted, and new memorials that augment or change the narratives told on our public landscapes. But I nod with understanding and approval when the mayor asks: “Why are there no slave ship monuments, no prominent markers on public land to remember the lynchings or the slave blocks; nothing to remember this long chapter of our lives; the pain, the sacrifice, the shame … all of it happening on the soil of New Orleans?” For half a century and more American historians of all stripes have written and taught newer, more inclusive, and yes, often darker histories such as Landrieu advocates. But it is essentially true that these histories of pain and tragedy, destruction and survival, do by and large await public memorials. They are receiving public museum exhibition and exposure. But in great civic monuments, not so much. The massacre in Emanuel A.M.E. Church in Charleston in June 2015 took America on this new tortured, surprising path to Confederate flag and monument removals. Where and when it ends Americans do not know. More than any other Southern politician, Landrieu has expressed this reckoning with the Civil War’s legacy in a newly eloquent honesty. Americans ought to debate how best to take up his call. Many great and challenging monuments, both old and new, exist in the United States. The world wars, the Irish famine, the Vietnam War, the civil-rights movement, the attacks on 9/11, the Holocaust, and even the Civil War itself have inspired brilliant works of public art. But Americans have to know more history in order to learn to think about them more imaginatively.