An Economist writer tells us the historiography of Gettysburg the site has changed.

When war memories were still fresh, that Pennsylvania town was a shrine to Union suffering. Confederate troops under Robert E. Lee invaded Pennsylvania to bring terror to Union territory. They seized farmers’ property and—in a monstrous touch—kidnapped free blacks and escaped slaves, sending scores southward into captivity. The war was still raging when Abraham Lincoln gave his Gettysburg address to dedicate a Union cemetery there, months after the pivotal battle outside town. So eager were locals for martyrs that Virginia “Jennie” Wade, a young seamstress shot by a stray bullet while baking for Union soldiers and the only civilian casualty of the battle, was pressed into service. The Senate granted her mother a war pension, and in 1900 an elaborate monument to her was erected, largely funded by the Women’s Relief Corps of Iowa, a Union state not represented at the battle.

Yet today, gazing at tourist shops full of Confederate battle flags, replica guns and souvenir T-shirts with slogans like “If At First You Don’t Secede, Try, Try, Again”, visitors to Gettysburg might suppose that the Confederates won. The same shops are piled high with Donald Trump hats and shirts, while Trump-stickered pick-up trucks and Harley-Davidsons rumble along the town’s narrow streets. The Jennie Wade House and gift shop flog Confederate knick-knacks, and—in an attempt at neutrality—tour guides stress the young woman’s friendship with Wesley Culp, a local youth who moved to Virginia and fought for the South.

Well that’s disgusting. I had no idea.

Merchants are following the market: in Trump-voting bits of white America, such as rural Pennsylvania, affection for the Confederacy has floated free of ancestral loyalties. Today the rebel cause stands for a chin-jutting, screw-you sort of conservatism. This extends to modern-day Iowa, home to a Republican congressman and anti-immigrant zealot, Steve King, who for a while kept a Confederate flag on his desk (later removed after a Confederate flag-waver shot two Iowa cops). The rebel flag means different things to different people, says a historian with the National Park Service in Gettysburg, tactfully. For all that, he understands, and quietly worries, if it makes black visitors uncomfortable.

No, sorry, that’s bullshit. A historian with the National Park Service should not be that kind of “tactful.” The “rebel flag” is what it is: the flag of an organized attempt to secede from the US in order to preserve slavery. Slavery. People don’t get to have their own special meaning for it that ignores the massive systematic rights-violation at the core.

It’s again popular on the left to say forget all this identity politics, focus on class instead, so that the battle can be over economic justice instead of all this touchy-feely identity stuff.

Yet the past offers a further lesson, one worrying for those on the left who are sure that the way back to power is to compete with Mr Trump’s fiery economic populism, while shunning his taste for racial controversies. For American history teaches that, once stoked, racial, ethnic and economic grievances are perilously hard to keep apart. In his fine history of the civil war, “Battle Cry of Freedom”, James McPherson records that many whites in Union states like Ohio, Illinois or Indiana were hostile to elites, bankers and blacks in roughly equal measure. Lots of unskilled workers, notably Irish and German Catholics, resented New England grandees for asking them to fight to free the slaves, and suspected that wealthy Yankees saw emancipation as a source of cheap black labour. Populists hated highfalutin newspapers as much as Mr Trump claims to today. In 1863 the New York Times borrowed three Gatling guns from the army to guard its head office as rioters protested against a military draft, yelling “Down with the rich!” and looking to lynch blacks.

Mr Trump, a man with a hazy, self-regarding sense of history, grasps that Them-against-Us rage has deep American roots. Opponents are free to hope that his ploys backfire. But for non-bigots, meeting him in any sort of populist anger contest is a trap.

Ditch the baseball caps.