One of the great open wounds of the black liberation struggle of the 1970s has finally been healed with the release of the last member of the Move 9, the group of radicals rounded up in a Philadelphia police siege in 1978 and held behind bars for more than four decades.

Chuck Sims Africa, 59, walked free from the Fayette state correctional institution in La Belle, Pennsylvania, on Friday morning. The youngest of the incarcerated group, he has been in custody since shortly after he turned 18.

His freedom marked his reunion with his family for the first time in almost 42 years. It was also historic, as it closed a chapter that had remained unfinished since the black power movement erupted in the late 1960s.

Alongside the Black Panthers, Philadelphia’s Move organisation was central to the volatile and at times violent struggle for black equality that lasted until the 1980s.

Members of the organisation regarded themselves – and still do to this day – as part of a family dedicated to race equality, with all members taking the last name “Africa”. Part Panthers and part eco-hippies, they also had a commitment to environmental justice that was ahead of its time.

Facebook Twitter Pinterest Chuck Africa upon his release. Photograph: Brad Thomson/Twitter

Mike Africa Jr, the son of two of the Move 9, said Chuck’s release put an end to a long and gruelling campaign. “We will never have to shout ‘Free the Move 9!’ ever again. It’s been 41 years, and now we’ll never have to say it.”

For Mike Africa, who is also Chuck’s nephew, the release was especially poignant. He was born in a cell five weeks after his mother, Debbie Sims Africa, Chuck’s sister, was rounded up in the 1978 siege and incarcerated – she gave birth to him unbeknown to the prison guards and kept him hidden with her in the cell for the first few days of his life.

The Guardian began investigating the prolonged imprisonment of the Move 9 in 2018 as part of an examination into black power behind bars. At that time all the surviving members of the group were still in custody in various Pennsylvania prisons.

Members of the group described in letters, emails and prison interviews how they had endured so many years inside while keeping their spirits high. Janine Phillips Africa said that she raised therapy dogs in her cell and grew vegetables in the prison yard, avoiding birthdays or holidays that reminded her of the passage of time.

“The years are not my focus,” she wrote in a letter to the Guardian. “I keep my mind on my health and the things I need to do day by day.”

Delbert Orr Africa said: “We’ve suffered the worst that this system can throw at us – decades of imprisonment, loss of loved ones. So we know we are strong.”

Soon after the Guardian began its investigation, the seven surviving members of the group began to be released on parole. First up was Debbie Sims Africa, set free in June 2018. “We are peaceful people,” she said as she stepped out of Cambridge Springs prison.

Then the other six began to emerge, one after the other like falling dominoes:

* Mike Africa Sr, October 2018

* Janine Phillips Africa and Janet Holloway Africa, May 2019

* Eddie Goodman Africa, June 2019

* Delbert Orr Africa, January 2020

Chuck Sims Africa completes the set.

The Move 9 were arrested following a massive police siege of their collective headquarters and home in Powelton Village, Philadelphia, on 8 August 1978. Hundreds of police officers in Swat teams armed with machine guns, teargas, bulldozers and water cannons surrounded the property following a long standoff with city authorities that saw the group as a threat to the community.

The siege culminated in a police shootout in which Move members allegedly returned fire though they denied doing so. A police officer, James Ramp, was killed in the crossfire.

Nine members were arrested and held jointly responsible for Ramp’s death despite forensic evidence showing he was killed with a single bullet. In 1980 the nine were convicted of third-degree murder and lesser offenses and each sentenced to 30 years to life.

Two of the nine – Merle and Phil Africa – died in prison. The remaining seven fought for many years to convince parole authorities that they were safe to be let out, pointing to clean discipline sheets in prison.

Over the past two years there have been no security incidents relating to any of the paroled individuals.

Wilson Goode, former mayor of Philadelphia, wrote to the parole board to support Chuck Africa’s bid for freedom. He said: “His release will reunite a family after 40 years and I am convinced he will be a positive contributing voice to the Philadelphia community.”

Goode, the first black mayor of Philadelphia, was in that position on 13 May 1985 when the second disaster relating to Move occurred. Following another prolonged bout of acrimony between the organisation and its neighbors and city authorities, the decision was taken forcibly to evict the group from its latest headquarters, then in Osage Avenue.

Another shootout broke out, and when that failed to flush them out police dropped incendiary bombs from a helicopter on to the roof of the building. A fire ensued which was allowed to spread, eventually razing to the ground 61 homes in the overwhelmingly African American neighborhood.

Eleven people in the Move house, including five children, died in the inferno. Chuck Africa’s cousin, Frank, was among the adults who were killed.

All the paroled members of the Move 9 are now preparing to mark the 35th anniversary of the tragedy. For the first time they will be able to commemorate the event and the relatives and peers they lost outside a prison cell.