When Nelson Mandela visited Boston in June 1990, just four months after his release from prison — he acknowledged the role of Bostonians in helping to weaken the apartheid government of South Africa and for his own freedom. Among those Bostonians credited by historians with helping to end oppression in South Africa is a former Cambridge High School teacher who took a risk.

Most drivers who whiz by the old Polaroid Corporation building on Memorial Drive in Cambridge may be unaware of the historical significance this institution is accused of playing in the prolongation for of the apartheid state.

You have to go back in time to the end of World War II to understand why.

South Africa’s National Party, led by doctrinaire segregationists, codified legislation known as "pass laws," which restricted where the black population could live, work, or move. And any white person could ask a black person for their passbook and that person was required to show it. In March 1961, a peaceful mass protest against the pass laws resulted in the massacre of over 60 people in Sharpeville in South Africa. But let’s jump ahead ten years to 1970 to this spot on Memorial Drive: Polaroid.

Two African-American employees here discovered that Polaroid was making the photographic products for processing the dreaded pass books. Caroline Hunter was one of them.

"I worked at Polaroid as a research chemist and my late husband Ken Williams was in the photo department producing advertisements for Polaroid, and one day I went to pick him up for lunch and we discovered an ID badge with a mockup of a black guy that we knew from Polaroid saying 'Union of South Africa Department of the Mines'," Hunter said. "We discovered that Polaroid was in South Africa and that they'd been there for quite some time, since 1938, and that they were actually the producers of the notorious passbook photographs which South Africans, black South Africans called their 'handcuffs.'"

Caroline Hunter and the man who became her husband, Ken Williams, protested the sales and in 1971 testified before Congress calling for a complete halt on the Polaroid's policy.

"Ken and I launched a campaign to find out what was going on, and eventually held a press conference and called for an international boycott for Polaroid to get out of South Africa; for Polaroid to turn their profits over to the liberation movements and to recognize the liberation movements in South Africa," Hunter said. "With the help of another South African, Chris Nteta, who's now deceased, we organized the first international boycott by black workers, by black people, by anybody in the world against South Africa, and that eventually led to the divestment movement that really weakened the South African government and allowed the blacks in South Africa a better chance of negotiating their freedom."

The congressional hearings into the role of American corporations in aiding the South African government became the basis for the divestment movement.

"And we were very aggressive in trying to get people to support the boycott, so Ken and a delegation of brothers went down to D.C. to see Congressman [Ron] Dellums," Hunter said. "He received them with open arms. He received the literature and information and he took that cause on to the Congress to publish and put forth this legislation for 17 or 18 years until they finally got both Republicans and Democrats to pass the sanctions bill that prohibited the US from doing business in South Africa."

After she was fired by Polaroid, Hunter went on to become a teacher and assistant principal at Cambridge Ridge and Latin, and last year she was honored with the Rosa Parks Award by the National Education Association for leading the effort that led to sanctions against apartheid South Africa. The divestment movement and sanctions crippled the South African economy. That led British Prime Minister Margaret Thatcher — who viewed Mandela as a terrorist — to tell her friend, South African President F. W. De Klerk, that the writing was on on the wall, and he subsequently freed Nelson Mandela in February 1990.

Caroline Hunter — whose life has been he subject of documentaries and books, is now writing her own story about the effort to hold a business accountable in the face of one of history's greatest human rights tragedies.

Basic Black remembers Nelson Mandela: