LOUISVILLE, Ky. — More and more Americans, educated 20-somethings and empty nesters among them, want to live downtown. Plenty of downtowns are coming back; many are thriving. Even so, we remain a nation in thrall to suburbs, highways, cars. On a recent visit here I was struck by this paradox.

A half-century or so ago Louisville, like so many American cities, bet the farm on cars and suburbia. It sacrificed a swath of its downtown to three interstate highways. There was the usual reasoning: highways would bring business, without which downtown, already struggling, would shrivel and expire.

Blocks of historic commercial warehouses and banks were leveled as a consequence; the center of the city was severed from Louisville’s spectacular waterfront; mass transit was largely abandoned and many corners of town transformed into parking lots. Around the same time the construction of a plaza and a hotel, along with a Mies van der Rohe building that commanded a singular view of the falls on the Ohio River, aspired partly to reconnect the city to the water. But the completion of the big John F. Kennedy Memorial Bridge leading into downtown capped off the massive entanglement of highways that produced what locals came to call Spaghetti Junction.

And the traffic?

It got worse.

Since then cities everywhere have been tearing down postwar highways that ripped through downtowns. They’ve replaced them with parks and streets and neighborhoods. It has happened from Seoul and San Francisco to Milwaukee and Madrid. In San Francisco removal of the Central Freeway has turned a destitute neighborhood into one of the most fashionable quarters of the city. Cincinnati (which is linked to Louisville by one of the interstates rumbling through downtown) and Pittsburgh have made headlines, too, successfully recovering historic riverfronts.