Margaret Douglas McCarter of Westport died Wednesday, Sept. 12, on Martha’s Vineyard. She was 86 years old.

Mrs. McCarter was born in El Paso, Texas, in 1926, and grew up in Pachuca Hidalgo, Mexico. She attended schools in Mexico and the United States. In 1949 she married Dr. Robert H. McCarter, a Boston psychiatrist, and together they raised five sons in Weston.

She was committed to informed participation in the political process. Her career as a political activist spanned more than 50 years, initially centering on disarmament, civil rights and the war in Viet Nam. She was a founding member of Voice of Women, PC Pax and Political Action for Peace; was an active member of the NAACP and Amnesty International; and participated in Martin Luther King Jr.’s 1963 March on Washington. She campaigned for politicians too numerous to list, from H. Stuart Hughes and other “peace candidates” of the 1960s to Bill Clinton. She was president of the Massachusetts Chapter of the Women’s International League for Peace and Freedom for nine years and served four years on their national executive committee.

During the 1970s she was a member of United Nations fact-finding teams sent to Chile and Nicaragua and was also appointed to a team inquiring into prison conditions in Northern Ireland. She testified on her findings before committees of the United Nations, U.S. Congress and British Parliament.

Her role in formal investigations into human rights violations led to her private development of strategies and contacts, which she used to effect the release of political prisoners throughout Latin America, including the Chilean minister and former ambassador to the United States Orlando Letellier, who wrote thanking her for his freedom just before his assassination in 1976.

Simultaneously, serving as an aide to Thomas O’Neill 3rd, she developed legislation to facilitate the assimilation of political refugees here in the United States. Between 1970 and 1979 she was a delegate at seven international conferences on human rights, disarmament, peacemaking and women’s rights in Columbia, England, Mexico, Spain and the United States. Through her activities on women’s rights, she came to know Madame Sun Yat-Sen, co-chairman of the People’s Republic of China, and in 1971 she inadvertently came to international attention when a telegram exchange between the two women was reported as the first instance of communication between a member of the Chinese government and a private citizen of the United States. In 1978 she was one of 250 women invited by the secretary of state to a briefing on the Strategic Arms Limitation Talks Agreement.

Her voice continued to be heard in her home town of Westport, at political meetings, and in letters to the editor until 2008.

She is survived by a brother, C.B.M. Douglas, and four sons: Harris, John, Brian and Bruce, and their families. She is predeceased by her husband Robert, her sister Sonya Douglas Wales, and her son Frank, who died on August 28, 2012. A memorial service will be held on Saturday, Nov. 10, 2012, at 1 p.m. at the Westport Friends Meetinghouse, 938 Main Road in Westport, Mass. Reception to follow. In lieu of flowers, memorial donations may be made to Women’s International League for Peace and Freedom (wilpf.org) or Amnesty International (amnestyusa.org).