Living in Greenwich Village and already familiar with leaders like Mr. Marshall and the Rev. Dr. Martin Luther King Jr., she became close friends with Black intellectuals like Mr. Baldwin, the novelist and essayist, and his brother David.

Thanks to the Baldwin brothers, Ms. Alexander was one of a small number of civil rights figures invited to a meeting in May 1963 with Robert Kennedy, the attorney general, in a New York City apartment.

For almost three hours, Ms. Alexander watched as Mr. Kennedy, who thought the civil rights movement was moving too fast, parried, harangued and argued with the singer Harry Belafonte, the playwright Lorraine Hansberry, Dr. Clark and others, until Ms. Hansberry got up and left in anger, with most of the rest following behind.

Though the meeting ended in acrimony and Mr. Kennedy later ordered the F.B.I. to tap James Baldwin’s phone, many historians see the meeting as a turning point for the attorney general, who by the fall was a leading figure in the push for the Civil Rights Act.

“June was there as history was being made,” Ted Shaw, a former president of the Legal Defense and Education Fund, said in an interview. “And she helped make it.”

June Shagaloff was born on June 14, 1928, in New York City and grew up in the towns of Merrick and Baldwin on Long Island, where her father owned several pharmacies. Her parents, Samuel and Gertrude (Bellinson) Shagaloff, immigrated from Russia in 1905.

June spent her summers at nearby Jones Beach, a public facility where she sometimes faced discrimination from people who assumed she was Black.