Cars ambled up and down Blue Hill Avenue as pedestrians darted back and forth across the street, stopping into stores such as Roxie Sales, Bookstein Drug, and the Grove Hall Dress Shop on a busy Friday night. It had been warmer than usual that day, but the heat had begun to break around 5 p.m., as a small crowd grew outside the welfare office near Seaver Street.

Inside were about 30 demonstrators, who had chained the doors and staged a sit-in. They refused to leave — or to let anyone else out, including the office staff — until their demands were met.

“We are tired of having our checks cut off without warning or investigation because of malicious gossip and lying officials!’’ read the handwritten flier. “We are tired of hostile social workers and supervisors!’’

The demonstration by Mothers for Adequate Welfare went off without a hitch — until it didn’t. It was a peaceful protest that turned violent in an instant, setting off a torrent of events that cascaded down Blue Hill Avenue 50 years ago, consuming 10 blocks, lasting for three days, and now lost to history for most Bostonians.

But June 2, 1967, is a day to remember now, the day that Boston joined what some deemed the period of “Urban Riots,’’ a five-year span in the 1960s that touched nearly every major city in black American’s fight for civil rights. New York. Philadelphia. Los Angeles. Chicago. Cleveland. Atlanta. But not Boston. Some thought Boston, with a black population of nearly 10 percent, was immune.

It wasn’t.

Old Boston was changing in many ways. With a new City Hall under construction, a spate of downtown construction, and even faint intimations of a miracle in the offing at Fenway Park, things seemed to be looking up on many fronts. But on race, the city was stuck, and not in a good place at all. Some neighborhoods were off limits to black homeowners. Jobs were scarce. Schools were blatantly unequal in their offerings. The divisions that would become obvious to the world with the school integration crisis of 1974, and its long ugly aftermath, were smoldering largely out of view in 1967, a fire awaiting a match.

The protesters’ flier asked people to “Join Welfare Mothers’’ at the Grove Hall Welfare Office, 515 Blue Hill Ave., and the welfare mothers’ demand was simple: Treat us with dignity.

Welfare was largely administered at the city level in that era, and the women gathering in Grove Hall had had it with disrespectful treatment that had, in their experience, become outrageously routine. Frustrations had reached a boiling point.

“These were the days where welfare workers could, unannounced, come to your house. They could come at night to see if you were sleeping with somebody . . . because you’re supposed to be single. That kind of stuff was going on,’’ said state Representative Byron Rushing, who was a community organizer at the time. “They were just fed up with the way they were being treated.’’

The sit-in started quietly that Thursday. The mothers, black and white, stayed overnight without incident, according to published reports.

An open window on the first floor allowed the women to occasionally lean out to chat with supporters and passersby. Rushing said he casually stopped by that Friday on his way to a birthday party.

“I go up just to see how everybody’s doing,’’ he recalled recently from his office at the State House. “We chatted for a while, and I can remember a guy from the ACLU came up to see how things were going. I said, ‘Looks fine. You can take off.’ ’’

The group of women, which by Friday night had grown to about 50, and included students and men, wanted an audience with the city’s welfare director, Daniel Cronin. He arrived at about 5 p.m and agreed to speak with the group if they would let him walk through the front door. They declined, demanding he speak to them in the presence of those outside.

The mothers would, in the end, demand 10 things from the welfare system, including representation on policy-making boards, benefits sufficient to allow them to save money for their children’s education, the ability to see social workers more than once a week, and Cronin’s removal.

It was, for the city, a daunting list. And the likelihood that the demands would be met before police would be called to roust the group from the welfare office seemed faint.

Former city councilor Chuck Turner, who was a community organizer at the time, was inside the building with the women and the welfare workers. Standing in the lobby, Turner recalled the atmosphere was charged with enthusiasm and anxiety.

They waited for a “police onslaught that we assumed was going to come,’’ he said. By Friday, he said, “there was a sense that they weren’t going to let people stay there all night.’’

What happened next remains a point of contention. Protesters, in interviews and published reports at the time, describe a starkly different picture than the one laid out in police reports and other city documents.

When police arrived, Turner and Rushing said, there was no back-and-forth about the protesters cause or their demands. No outreach to leaders of the black community. No negotiations with those inside, just a phalanx of police officers who violently reclaimed the building, protesters said.

“Now beat them. Let them have it,’’ was the order given, one of the mothers’ group’s organizers told WGBH days later.

The trigger for police may have been reports that a social worker inside the office was having a “heart attack,’’ according to published accounts of the protest and subsequent rioting.

“I think we might have been prepared to wait it out, but I believe the report about the sick woman motivated our move,’’ a veteran officer, who was not identified, told The Boston Globe at the time. “We had to get her out.’’

The welfare office’s front doors were chained shut, so police officers slammed themselves into the doors of the building, shattering glass and storming inside.

“I look up, and they are pulling these women out,’’ Rushing said. “They are literally dragging these women over glass, broken glass.’’

A woman, according to the Bay State Banner, screamed out of the window, “They’re beating your black sisters in here.’’

People watching from across the street erupted in fury. They rushed forward in an attempt to free the women. Rocks were thrown. More officers arrived, outfitted in riot gear and carrying rifles.

Rushing said he tried to find a supervising officer in hopes of de-escalating the increasingly inflammatory situation. As he began pleading with a police officer, he recalled, another one hit him in the head with a nightstick.

Bleeding. Disoriented. Handcuffed.

“I’m arrested,’’ he recalled. Turner wound up under arrest as well.

Police reports from the day tell a different story.

Deputy Superintendent Joseph Saia of the Boston Police Department wrote that he arrived about 5:20 p.m. to find “about two hundred negros, male and female with few whites scattered among them . . . milling about’’ in front of the welfare office. Officers were already inside trying to “reason with the demonstrators to no avail.’’

About 40 minutes later, after more officers arrived, Saia wrote, he asked one of the Grove Hall office employees to demand that the protesters leave. When they refused, he ordered police to remove them.

“As the detail was carrying out my order, they were punched, kicked, bitten and thrown to the floor during the melee that erupted,’’ the report said. “As the police officers were coming out of the building with their prisoners, rocks, stones and bottles were thrown at the officers by the demonstrators in the street.’’

Only after civil rights leaders began to arrive and tried to calm the erupting rage, did officers begin to escort the employees out — including the 55-year-old social worker who needed to be taken to “Boston City Hospital and treated for a heart condition,’’ according to Saia’s report.

Whatever the exact sequence of events and causes, a seal had broken, and the anger in the neighborhood couldn’t be contained, spilling down Blue Hill Avenue. Windows were smashed. Stores looted. Buildings burned.

Grove Hall was once a bustling commercial district, home to most of the city’s growing black community. “About 65,000 Negroes and Puerto Ricans reside in Grove Hall area,’’ the Globe reported at the time.

The city’s black population had tripled since 1940, when it was just 3 percent of the population, but it remained relatively small — and confined. Few black people lived east of Columbia Road and south of Franklin Park. Boston’s Jewish community, which had long called Blue Hill Avenue home, had begun receding south into Mattapan.

“People don’t appreciate how segregated and how much tension there really was among the various racial groups,’’ Turner said. Open clashes were common in much of the city, he said, wherever turf was in dispute.

Amid the furniture stores, dress shops, pharmacies, delicatessens, and hardware stores that packed Blue Hill Avenue, several civil rights organizations had storefront offices. Operation Exodus. Congress of Racial Equality. Northern Student Movement.

The section of Blue Hill Avenue in Grove Hall was known as Civil Rights or Agency Row, and it wouldn’t have existed “if it was all sweetness and light,’’ said Sarah-Ann Shaw, a community organizer who became Boston’s first black female television reporter in 1969.

Still, some community leaders, middle-class blacks, and white elected officials thought Boston was not vulnerable to the turmoil roiling the rest of the country in the fight for civil rights.

“The reason the people didn’t think it was going to be as bad in Boston is because there weren’t as many black folks, people of color, and poor whites living in that district as there were in other cities,’’ said Dan Richardson, the former director of HUD’s Boston office who was an organizer for American Friends Service Committee in 1967. “A lot of people thought these things could only happen where there were huge, masses of people of color. And they were wrong.’’

Life had not been easy for people living in the community, he said.

Whites who could afford to leave had begun moving out of the city in search of suburban life and better jobs, creating openings for blacks in an economy they had long been largely shut out from, community activists said. Still, the blue-collar jobs that were available to black people in most cities tended in Boston to be the preserve of the city’s white ethnic groups — Jewish, Italian, Irish, Polish, and Yankee — leaving less opportunity for the city’s growing black population.

“You had to fight to get a janitor’s job,’’ Rushing said.

There were a handful of black police officers, few black teachers, fewer principals, and hardly any black MBTA drivers.

It was against the harsh backdrop that tensions festered, awaiting a moment and focal point — and Grove Hall was it. “Folks decided to liberate the welfare office,’’ Richardson said.

“People expressed horror and shock and a total lack of understanding of what was going on, but all they had to do was look at the facts. And the facts were that people weren’t getting what they were mandated under the law. They were not getting housing. They were not getting education. They were not getting jobs,’’ he said. “That three-headed, four-headed monster was there all the time.’’

And it showed its ferocious face the first weekend in June. As the uproar spread from the office to the neighborhoods, many of the civil rights and other agencies stayed open as Friday night became Saturday morning, hoping to stave off more mayhem.

“There were a lot of crazy things going on in the business district, which got shut down,’’ Richardson said. “We wanted to make sure no one was hurt. We wanted to make sure transportation was moving. We wanted to make sure that things stayed as normal as possible.’’

But nothing was normal that weekend.

The turmoil reigned for three days, an uneasy calm receding into chaos Friday as day turned to night. Blue Hill Avenue had been closed to traffic between Seaver and Dudley streets. Bricks were thrown at police cars and fire engines. There were reports, never confirmed, of snipers shooting at police from roofs. Police fired warning shots in the air. There were no deaths, but a firefighter was shot in the wrist Saturday night.

Business owners were caught in the middle of it all.

Barry Alpert was a 19-year-old student at Northeastern University when his phone rang that Friday night. It was his then-girlfriend (she’s now his wife of 45 years), wondering if he could go with her father and brother to secure the family’s optometrist shop at 303A Blue Hill Ave.

Alpert’s father-in-law, Saul Rosemark, who lived in Milton, had gotten a call from a neighboring business, alerting him to the riots and looting in Roxbury. The air conditioner in Rosemark’s shop was gone, torn out, leaving a gaping hole above the front door. Could he help board up that opening?

“Sure. What else do I want to do in the middle of a riot?’’ the 69-year-old deadpanned in a recent interview. “So we went down there, and it was quite unnerving to say the least.’’

There was little damage to Rosemark’s 30-year-old practice, save for the stolen air conditioner.

The rest of the block didn’t fare as well. Fires raged at Warren Furniture Store and Cohen’s Furniture Mart. A television store was looted. There was an explosion at Ashmont Supply Co., a hardware store that often employed young men from the neighborhood. Everything inside was demolished and destroyed.

“Then the crowds moved down my way,’’ said John Jones, 86, whose barbershop had been at Fayston Street and Blue Hill Avenue for three years when the riots began. “I was right in the middle of it.’’

As darkness fell Friday night, he watched the streets fill up with people. He watched the mob flip over a car then set it on fire. He ran outside, and with the help of several other men, pulled the man from the car and got him to the hospital.

Spectators ran inside his shop, seeking shelter from flying rocks. Boys ran through his shop after looting the liquor store next door, trying to stash their take in the back alley. Then came the police. But instead of nabbing the thieves, they grabbed Jones’s son.

“No, he belongs here!’’ Jones remembers yelling, holding one of his son’s arms while a police officer held the other. A local boxing promoter who happened to be there intervened, and Jones said, “They turned my son loose.’’

After that he locked the doors but didn’t go home. “I was scared they were going to burn my shop,’’ he said.

Jones, his son, and his nephew, who also worked in the shop, stayed for three days. At one point, Jones asked police officers not to stand in front of his shop, as crowds were throwing rocks at officers and he feared they’d miss and shatter his windows.

Guarding his shop — and others in the area — became the responsibility of a local group he belonged to called Afram Associates, which served as something of a community development organization started by black businessmen.

“My guys got out there and patrolled the block and let the rioters know, ‘You don’t cause any problems on this block,’ ’’ he said. “And the stores on my block were spared.’’

By Monday night, calm had returned to what the Globe referred to as “the predominently [sic] Negro’’ section of the city. But the physical and social destruction had been wrought. Neighborhood businesses filed more than $1.3 million in claims. But the city paid out about $240,000, reimbursing businesses only for damage — not missing, stolen, or looted items. Many business owners did not return to the neighborhood.

A message had been sent to the city, but Jones said he’s not sure what good came from the weekend of unrest. The rioters, in his view, weren’t just seeking justice but also something to steal. They “didn’t have anything to lose,’’ he said. “Rioting was a means for them to gain something that they thought was valuable.’’

Power and dignity for black Boston would remain elusive.

Some small reforms came to the city’s welfare department, such as the creation of welfare substations to relieve crowding at the Grove Hall office. But the main fights would stretch far into the future in Boston and beyond — for better schools, more jobs, higher wages, a fair shake in the courts, and access to the halls of power. Change would be painfully slow, and still is. The riots of 1967 would slip swiftly into memory; frustration and anger would long outlive them.

“We thought that our efforts would change things overnight,’’ Shaw said. “We thought we would wake up tomorrow and people would not be living in substandard housing, kids would not be going to bad schools. We thought because we were working so hard . . . that change would come.’’

By Akilah Johnson | Globe staff

Akilah Johnson can be reached at akilah.johnson@globe.com. Follow her on Twitter @akjohnson1922.