Sally Mary Caroline Belfrage, independent leftist, world traveling journalist, and author of five books, was born in Hollywood, California on October 4, 1936. The daughter of Cedric Belfrage and Molly Castle, two radical British writers, she moved with her family in 1942 to the New York city area where they stayed until 1955. She went to Bronx Science High School, and briefly attended Hunter College. During their time in New York, Cedric started the independent weekly radical newspaper The National Guardian, Cedric and Molly were divorced, Cedric was arrested, and by 1955 both were deported under the provisions of the McCarran Act. Although an American citizen, Sally left with them. In London, she attended the London School of Economics and worked in publishing. In 1957, she attended the World Youth Festival in Moscow, where she then worked (editing English translations of Tolstoy) and lived for the better part of a year. During her stay she took part in a six-week tour of China, and appeared in a Russian movie, "Memories of the Heart."

Upon returning to London, she wrote her first book, A Room in Moscow (1958). While on a 1959 U.S. publicity tour, she befriended folksinger Millard Lampell, who encouraged her to visit Israel. Thus began another year of travels throughout the Near East, during which she worked on a kibbutz, met King Hussein of Jordan, and in 1960 married Sari Nashashibi, a Palestinian, so he could obtain a U.S. visa. Upon her return from the Near East; she spent the next two years traveling all over Europe (with Benjamin Sonnenberg, founder of the magazine Grand Street) before moving to New York in mid-1962.

In 1963 Belfrage traveled to Georgia and North Carolina to research the civil rights movement, and was inspired to participate in the SNCC-sponsored Freedom Summer organizing drive of 1964. She was assigned to Greenwood, Mississippi where she helped start a literacy school and a community library, participated in a voter registration drive, spent several days in jail, and went to the 1964 Democratic National Convention with the Mississippi Freedom Democratic Party delegation. Her memoir Freedom Summer was published in 1965.

In November of 1965 Belfrage married playwright Bernard Pomerance (author of The Elephant Man). In 1967 her daughter Eve was born, followed in 1969 by her son Moby. After the latter's birth, the four began renting the flat at 51 Randolph Avenue in London that was to remain Sally's home until her death. In 1970, she helped found a community-based "Women's Liberation Group" which remained in operation for more than twenty years. In 1980 she published Flowers of Emptiness, about her 1976 experiences during two-month visit to a guru's ashram in India. In 1975, Sally and Bernard Pomerance separated and he moved to the United States.

In 1983-1984 Belfrage was involved in the Greenham Common Women's Nuclear Disarmament movement, and helped edit its broadsheet "The Greenham Factor." Also in 1984, she began to visit Belfast, Northern Ireland, to research the effects of the longstanding civil conflict on Catholic and Protestant women. The resulting book, The Crack: A Belfast Year was published in 1987. The remainder of Belfrage's life was spent traveling and writing her coming of age memoir, Un-American Activities, published in 1994. She died of cancer in London in March 1994.