Gentrification can often gestate invisibly for years, and in the mid-1980s, as Mr. Patterson founded the Tattoo Society of New York and opened up the Clayton Gallery on the first floor of his home, The Village Voice was already reporting that major developers like Helmsley-Spear were investing millions of dollars on vacant lots and abandoned buildings in the neighborhood. Even as local rents began to rise, Mr. Patterson’s arts space was showing work by nontraditional artists like Hasidic Jews and the leader of a local motorcycle gang. Here were the conflicted seeds of an eventual transformation: On the one hand, corporate money was pouring in; on the other, Mr. Patterson was making custom baseball caps for rebel celebrities like Matt Dillon and Gus Van Sant.

Then, on Aug. 6, 1988, hundreds of downtown residents clashed with the police in Tompkins Square Park in the East Village. The nominal issue was a 1 a.m. curfew imposed on the park, which had turned into an encampment of the homeless and a gathering place for what were described by many as skinheads, drifters and rowdy youths. As darkness fell, officers in riot gear descended on the crowd, and a nightlong melee followed. The park that night turned into something like “a war zone,” The New York Times reported; more than 100 complaints of police brutality were lodged; and Mr. Patterson caught it all on tape.

It was, in a sense, the height of his career as a documentary artist. The networks showed his footage on the nightly news, and journalists and academics called on him for quotes. While Mr. Patterson was able to capitalize on the attention and channel it into projects that later included a well-received photo exhibition, “L.E.S. Captured,” and a multivolume history of the Lower East Side’s Jews, for him the riot marked the moment when the city’s business interests and security apparatus joined forces and, in so doing, made New York unlivable.

It took another quarter-century for progressives in the city to catch up with Mr. Patterson, who stayed in New York despite its metamorphosis, with an obstinate belief that if he couldn’t counteract the creeping corporatization, he could at least manage an existence on its margins. Twenty-five years is a long time to live on hope; but a few months ago, just as it had finally died, something happened to restore it.

But first, there were more losses.

In July 2011, the Mars Bar, a notorious dive on East First Street that Mr. Patterson frequented, closed its doors and turned into a TD Bank branch. A few months later, the Life Cafe, where an acquaintance, Jonathan Larson, wrote a portion of the musical “Rent,” was suddenly shut down. Last year, it was the artists’ bar Max Fish, which decamped to Williamsburg, Brooklyn, prompting a devastated Twitter fan (not Mr. Patterson) to write: “Final nail to the post-punk guts of upper Ludlow Street’s coffin.”

But perhaps the cruelest blow of all was the death last May of Taylor Mead, an artist and actor who rose to fame in the 1960s after starring in a series of underground films by Andy Warhol. At age 88, Mr. Mead was forced from his home on Ludlow Street, where he had lived for more than 30 years, after battling his landlord, who was converting the building into market-rate apartments. He moved to Colorado and within a month he had died of a stroke. When Mr. Patterson got the news, he was crushed.