In its prime, US Route 40 was America’s Victory Highway. It ran from New Jersey to California, its dusty signs and roadside attractions — from the muffler men to metaphors rising in the desert — providing an American iconography. Along with its sibling, Route 66, Route 40 provided an echo of the American frontier; the nation’s families could pile into their tailfinned chariots and stick a thumb in Frederic Jackson Turner‘s eye, if only for the space of a vacation. But at the end of June, 1956, Dwight Eisenhower created the interstate highway system with the stroke of a pen, and Route 40 began its slide into irrelevance. In 1964, California decommisioned Route 40; it was a national highway no longer. The diners and flyspecked tourist traps remained to be examined by students of Americana, but the towns that relied on the commercial traffic of Route 40 were doomed. Brownsville, Pennsylvania is a ghost town in a way that not even the distressed steel towns like Alliquippa can quite match up to; its attractive downtown has simply been boarded up and abandoned, perhaps in hopes that its stretch of US 40 will one day hum with commerce again. But when cities lose their commercial reason for being, when jobs go away, they tend not to come back. Mining towns out west and in the Far East don’t have much reason to exist once the mines aren’t being worked. Diesel engines killed the need for pump towns along the railroad lines of rural America. Engines have been the lifeblood of Motor City, USA since Buick started making them there in the nineteenth century, but as industry has moved away from Detroit and Flint, little has sprung up to replace it. Ruins can coexist with a thriving city, but the slow depopulation of postwar Detroit (dramatically accelerated by white flight after the riots of the ‘60s and ‘70s) has left a hollow city, and neither the population decline nor the disappearance of the city center has stopped yet. A thousand years ago, the Fremont people vanished, leaving their ruins — whole towns, in some cases — behind them. Five hundred years ago, the Khmer empire began to disintegrate, with the amazing ruins of Angkor Wat remaining as a remnant of their power. Living cities don’t have abandoned lots taken over by farmland, because living cities have a reason to exist. When the reason goes, the people go, and the weeds and the rats move in. Without their purpose, cities revert to jungle and prairie. If Detroit’s fate will be that of Angkor Wat and Pumpville, Texas, what stories will we tell ourselves to explain where it went?