Here, along a seamless stretch of small-city blight, a deserted storefront had held its own. With 9 of its 10 front windows broken, it fit in among the two boarded-up bank buildings, last used as houses of worship, and the abandoned Jimmy’s Custom Cleaners, whose claim to being open remained true, since you could stroll right into the emptiness.

Finally, a year or two ago, demolition workers knocked down this Highland Avenue building in a municipal act filed somewhere between reclamation and surrender. But in doing so, they uncovered a rare portal to the faraway past, when boys wore knickers and Highland Park was the vibrant home of the Ford Motor Company’s first moving assembly line.

The demolition revealed two colorful, well-preserved advertisements that had adorned the brick side of the adjacent building for nearly a century. Their two-story assumptions of endless prosperity are particularly conspicuous in the Highland Park of today, a city so economically distressed that it recently removed most of its streetlights.

One of the ads spells out the long-gone clothing brand of Honor Bright in bold red letters floating in sky blue, along with the blurb: “Boys Blouses, Shirts and Playsuits for Real Boys From Morn ’Till Night.” It depicts two youngsters, both in ties. One, holding schoolbooks, wears knickers and a newsboy cap; the other, riding a bicycle, wears a faintly maniacal grin.

Nearby is another ad, for “A Thoro-Bred Work Shirt” called Black Beauty. Against its golden backdrop stands an older boy in his late teens, exuding the confidence to take his place in the assembly lines of Highland Park or, perhaps, the front lines of the Great War....