By the time it played its last show, 30 long-but-gone-just-like-that years ago in Detroit, Black Flag was a fairly complex cultural signal. The merciless vision of bandleader Greg Ginn had proved expensive in terms of personnel (Black Flag by the end was a band with more ex-members than members) and the abstracted furies of his guitar sound had shoved the music through mutation after mutation, from the riot-starting supra-Chuck Berry revvings of 1979’s “Nervous Breakdown,” through a mid-period intestinal art-crawl (“Scream,” “Nothing Left Inside”), to the punk-metal perversions that by 1986 comprised the bulk of the band’s live set.

Freaking out on his private frequency, Ginn was playing some of the wildest solos of his career, the hired-gun rhythm section of C’el Revuelta and Anthony Martinez plugging away gamely behind him. Meanwhile frontman Henry Rollins, having survived years of semi-ritualized beatings, burnings-with-lighters and stabbings-with-sharp-objects at the hands of his audience, was now a reconstituted Dionysus: bare chest, bare feet, rocking and lunging on splayed toes, with a predator’s tension or fixity in the upper body. And everyone had long hair. What exactly was this?

In the beginning, in the crucible of the Los Angeles punk scene at the turn of the ‘80s, there was no mistaking what Black Flag stood for: Opposition. To everything. I don't care what you have to say/ It makes no difference anyway, sang Groucho Marx in Horse Feathers, with jaunty nihilism. Whatever it is [BOMP!] I'm against it. Or to put it in Black Flag's terms: I wanna live/ I wish I was dead. The riffs were prophecies, the solos were freedom, the shows were bloody, and the lyrics were the wound of existence itself: Depression's got a hold on me/ Depression/ Gotta break free. Unbearable sensitivity was expressed with unanswerable power.

The songs broke their own toppling, tearing momentum with catastrophic time-slumps. Between songs, bassist-bodhisattva Chuck Dukowski would walk in tight, furious circles, silently shouting. The band didn't look like punk rockers; they looked like recently fired janitors. But L.A. is a horizontal city, and Black Flag's music blew holes in the ideological field, such that everything in a 30-mile radius that wasn't nailed down—every surfer/skateboarder, druggie, skinhead, indigent artist, curious soul, and every rejected emotion—came rushing into the breach. The LAPD took an oppressive interest, regularly —and violently—shutting down shows. (This fucking city/ Is run by pigs!) Black Flag worked very hard, penitentially hard, somehow combining vast amounts of not giving a fuck with a non-stop underdog campaign of snarling self-promotion.

And behind or below it all was the riddling, inaccessible intelligence of the artist Raymond Pettibon, Ginn's younger brother. Pettibon had given the band its name, its logo—the infamous and ubiquitous bars, four black rectangles offset to represent the rippling of a (black) flag—and, via the flyers that he designed and that were then splattered all over L.A. to advertise upcoming shows, a graphic identity that amounted to a kind of poetic molestation. Weird sex jokes; hideous boisterous cheerleaders; Jesus figures; Manson figures; authority figures; a black man with a demonically erect penis hoisting a terrified little white cop over his head: In Pettibon’s flyers a personal netherworld of imagery seemed to conjoin with the Californian id at its most chaotic level.

Doesn't it all sound like another world? It probably was. To foist your bohemia on an indifferent public, to harrow the complacent, to shake it up ... Joe Carducci, the outsider intellectual who helped run Black Flag's label SST, takes the long view: “Our closing frontier,” he writes in his 2008 memoir Enter Naomi, “was the sixties cultural revolution as it died out in the seventies and early eighties. In retrospect the Black Flag/SST story looks like a cultural analogue to the Manson-Weathermen-S.L.A.-Black Panther-Nixon White House-People’s Temple endgame—art just had more life in it than crime or politics or religion.”

As to the legacy: Black Flag, going from town to town in its smelly and tightly-packed van, built almost single-handedly the touring circuit that would sustain American independent music for the next 20 years. SST released albums by the Minutemen, Meat Puppets and Hüsker Dü—some of the greatest rock music ever made. Henry Rollins—actor, spoken-word performer, talking head, global witness—has become a superb figure in American life. And a generation of music fans carries the psychic imprint of the Black Flag live experience.

“There was a part of just about every song,” devout roadie David “Davo” Claassen told me in 1997, “that would pull back and fucking strike out like a cobra, and you'd be slapped upside the head. It was a physical reality that you had to get to grips with. That was their musical gift to the world. The fact that it got sensationalized along the way because of the punk phenomenon, and that it now has marketability or whatever—it all strays from the fact that it had an intangible substance that everybody fucking strives for in their art. And it dished it out in big old fucking shovelfuls.”