Yet the work of the top graffiti writers of the 1970’s and early 1980’s, which by some estimates includes several dozen at most, documents a crucial component of early hip-hop culture. That culture – where teenagers without bands made music by mixing song snippets and artists without studios painted entire subway lines – has since become a worldwide (and multibillion-dollar) phenomenon.

Its influence is such that some techniques originated by graffiti writers are now commonplace. Ivor L. Miller, author of Aerosol Kingdom, noted how the sides of buses in some cities are covered with a single advertisement. Even in New York, celebratory signs for the Mets and Yankees have festooned trains.

“It has been co-opted by corporations to sell products,” he said. “Those advertisements subvert the very logic of the system. When you see whole cars covered with an ad, that’s O.K. because it’s paid for. It’s not done by kids from the street.”

“Remembering and Defending Subway Graffiti”