The days that followed were a period of sadness and shame unlike any in the city's history, the start of a civic funk that lasted for nearly a decade.
The disaster cost Philadelphia millions of dollars, with the final bill yet to be tallied. And it destroyed the reputation of the city's first African American mayor, W. Wilson Goode, once hailed as the embodiment of racial reconciliation and managerial competence.
But somehow, someway, the MOVE disaster did not become the city's defining moment.
To a degree unimaginable while the ruins were smoldering, the stigma has faded.
The memories of that distant spring still haunt those most directly involved - the survivors, the neighbors, the police and the decision-makers.
Yet Philadelphia again hears itself called the City of Brotherly Love, a label it seemed to have forfeited for all time.
No longer do outsiders link the place to the image of a helicopter hovering over a rowhouse, and an outstretched hand releasing a black bag; they're far more likely to associate the city with Allen Iverson than Wilson Goode.
A recent, 654-page history of Pennsylvania disposed of the MOVE debacle in 78 words.
The impact of the disaster has receded for reasons other than the passage of time, although that's a big part of it. The Rodney King riots, the Ruby Ridge shootings, the Waco confrontation, the Oklahoma City bombing, and the 9/11 attacks - all dwarfed MOVE in terms of historical significance and, in most cases, body count.
"What so shocked and appalled us at the time was how government got it so wrong, the ineptitude, the miscalculation, the miscommunication," said lawyer Carl Singley, who helped investigate the disaster. "Compared to other incidents that have happened since then, I suppose, MOVE starts to pale."
And in the 1990s, enough good things happened in Philadelphia to make residents start feeling better about their city, and the country to view it in a more positive light.
Said J. Whyatt Mondesire, president of the local NAACP, "I don't think anyone under 25 years old can tell you anything about MOVE."
The story of what happened that day sounds no less preposterous now than it did then.
Who in his right mind would drop a bomb on a house, then not fight a fire? Why wouldn't all of the people inside leave a burning building? How could a city run by a black mayor do such a thing to a black group in the middle of a black middle-class neighborhood?
"It makes no sense, even today," said William H. Brown 3d, the lawyer who chaired the probe into what happened. "Every time I think about it, the angrier I get. There was no reason to drop that bomb. Whatever people thought about the MOVE adults, there were children inside that house."
The two sides - the city government and MOVE, an eccentric, self-described back-to-nature group obsessed with defending itself against the world - had clashed once before with deadly results.
In that 1978 confrontation, a police officer, James Ramp, was killed and several of his colleagues were wounded. And a MOVE member was beaten and kicked by police in full view of news cameras.
Nine MOVE members were convicted of the killing, even though there was some dispute whether any of them fired the fatal bullet. Eight of them remain in prison today; the ninth died of cancer in 1998. The officers involved in the beating were acquitted of all charges.
So when the remnants of the organization regrouped several years later at 6221 Osage Ave. - and began fortifying the house, brandishing weapons, and berating the neighbors with obscenity-filled tirades day and night - Round 2 seemed all but inevitable.
Which is not to say that it had to turn out the way it did.
In the aftermath, city officials would be second-guessed for their hurried, secretive planning and for their failure to grab the MOVE children before the assault - a step that would have been legally and logistically feasible because the children went to a park regularly.
And the radicals would be accused of having used the children as shields, needlessly exposing them to a fate they were too young to choose for themselves.
At dawn on that day, with the neighborhood evacuated and 500 police in place, Police Commissioner Gregore J. Sambor grabbed a bullhorn and announced: "MOVE, this is America! You have to abide by the laws of the United States!"
The police had warrants to arrest the adults on weapons charges. Sambor gave them 15 minutes to surrender. They replied through a bullhorn of their own: "You be sure you call your wives and your family, 'cause you ain't coming home!"
Shortly thereafter, a wild gun battle broke out. In the next 90 minutes, police fired 10,000 rounds of ammunition. And teams of officers, working from adjacent homes, used small explosive charges to try to penetrate the headquarters.
The assault failed. There was no Plan B.
As the hours passed, Sambor and Managing Director Leo A. Brooks, a retired Army brigadier general, came up with what Sambor later called, without irony, "the safest and most conservative plan." That was the bomb, the goal to destroy a makeshift bunker atop the house and blast a hole for tear gas.
From the command post, Brooks telephoned Goode and told him of the idea. The mayor was at City Hall; he had not gone to the scene all day. One reason, he wrote in his 1992 autobiography, was that he had been told that "unknown members of my own police force had targeted me for death."
Goode gave his consent, although he said a few days later that he didn't consider the device a bomb or know about any helicopter: "If . . . someone called on the telephone and said to me, 'We're going to drop a bomb on a house,' would I approve that? The answer is no."
At 5:27 p.m., the bomb, made from the mining explosive Tovex and the powerful military explosive C-4, was dropped. It didn't damage the bunker or pierce the roof; it did start a small fire.
Early on, that fire could have been fought and almost surely put out. But it wasn't.
"The decision was made to let the bunker burn," Sambor said later, recalling a conversation with Fire Commissioner William C. Richmond. "I made the recommendation, and it was concurred in by the fire commissioner."
Goode, watching on a television with snowy reception but not in constant communication with his field commanders, thought the fire was being fought.
The roof was allowed to burn for 45 minutes before the fire hoses were turned on; by then it was too late. The blaze was working its way down through the MOVE house and starting to devour the block.
As the magnitude of the disaster became apparent, a few MOVE members tried to leave the rear of the building. Some turned back, although police denied firing at them.
Two people got out alive: an adult woman, Ramona Africa, and a 13-year-old boy then called Birdie.
"I firmly believe that more people got out than Birdie and Ramona [and didn't survive] - that's one thing that still nags at me," said Brown, who chaired the MOVE probe. "I believe that someone, someday, will deliver a deathbed confession about what really happened."
Throughout the evening, the flames advanced, killing those in the house and leaving 250 neighbors homeless.
Overnight, the city became a laughingstock.
Television host David Letterman opened his May 14 monologue by saying: "I just want to know one thing. Does this mean MOVE won't get its security deposit back?"
USA Today printed an editorial cartoon of Goode as a fighter pilot wearing a leather helmet, sitting in the cockpit of a plane. It was quite a comedown for a man who had been considered for the Democratic vice presidential nomination 11 months earlier.
Later that year, the special commission that Brown headed conducted an investigation complete with televised hearings.
In its report, issued in March 1986, the commission berated Brooks for his passiveness, Sambor for his irresponsibility, Richmond for his acquiescence, and Goode for abdicating his responsibilities to lead. As for the bomb, the commission called it simply "unconscionable."
After weighing conflicting testimony, the commission concluded that police had fired at MOVE members trying to escape. A grand jury said otherwise in 1988.
The mayor responded to the report with a tearful apology, and there was speculation that his political career was over. Twenty months later, he won a second term, although he had lost much of his effectiveness.
Wilson Goode is now an ordained minister, known for his good works. He no longer talks about May 13, 1985.
"It never should have happened, but you can't unlive it," Richmond said recently. "The operation should not have gone forward that morning without knowledge that the kids were out of there."
No city official or employee ever faced criminal charges in connection with the MOVE deaths. But Ramona Africa was convicted of riot and conspiracy for her role and served seven years in prison.
After she got out, she and the relatives of two of the dead went to court and won a federal civil-rights judgment against the city worth $1.5 million.
The stigma has faded. It has not disappeared.
The anniversary is a reminder, as is the unresolved litigation over the rebuilt homes.
"It's like a chronic disease that goes dormant for a long time before you wake up and the pain is there again," said Thad Mathis, a professor of social administration at Temple University. "It's a metaphor people use at times in connection with whatever seems worst about Philadelphia or its leadership, as in, 'What do you expect from the city that dropped a bomb on a neighborhood?' "
But the pain recurs less frequently now; the metaphor is invoked less often. One reason, hindsight tells us, is that the debacle represented the end of an era, at least in some ways.
In 1985, the police department was a predominantly white institution that had been long distrusted by much of the African American community.
In fact, some black leaders maintained in the months after May 13 that the department's insular culture and racial insensitivity were more to blame for the disaster than Goode's failure to take charge.
Regardless of the validity of that claim, the department was transformed, diversifying and reforming itself up and down the ranks. Nothing remotely akin to the MOVE confrontation has happened here since.
"It's not the marker, Philadelphia equals MOVE, that it was, say, 15 years ago," said Randall M. Miller, coeditor of that 654-page history book, Pennsylvania: History of the Commonwealth. "When you look back, it's somewhat of an aberration, fascinating for the oddity, the stupidity, the callousness and the tragedy."
One of the odder sidelights of the saga is that another historic event took place in Philadelphia on May 13, 1985, an event that had at least as much impact on how the place would evolve in the next 20 years.
At midday, business leaders broke ground in Center City for One Liberty Place, the city's first true skyscraper. The ceremony marked the end of the restrictive gentlemen's agreement that no building could be taller than William Penn's hat on the statue atop City Hall.
This should have been a moment of triumph for Goode, a piece of progress he had helped make happen. But he could not attend. He was busy creating a different sort of legacy for himself and for his city.
Contact staff writer Larry Eichel at 215-854-2415 or firstname.lastname@example.org.