When Henry Chalfant arrived in New York City from suburban Pittsburgh in 1973, as an aspiring sculptor, he found a place teetering on the verge of bankruptcy. This was “Ford to City: Drop Dead” New York. But amid the turmoil a new form of art making was taking shape — one that took up space where it could, which was mostly everywhere.

As a typographical language, graffiti was still raw, a new kind of American expressionism rooted in the volatility of street life, largely done by kids living on the city’s margins. The urgent scrawls of names, crowding one another for visual dominance, was a form of branding as self-determination. Within a few years, styles became increasingly baroque, entire flanks of subway cars sheathed in florid top-down murals, hurtling the city’s overlooked periphery into its pulsing center.

Mr. Chalfant, now 79, credits one such piece, a Lee Quiñones burner from 1977, for permanently shifting his attention. “I came up to the Bronx, and I saw two cars painted by Lee and the Fabulous Five crew,” Mr. Chalfant said in a recent interview. “And I thought, Oh my god, I have to get that.” And he did, though it took 10 pictures. “From there I knew I was going to see this out,” he added. “ I found the contrast between what I was doing as a solitary studio artist and what I clearly needed in my life, which was more engagement in the world, and this is how I found it.”