Marion G. Merrill, 97, a civil rights activist and writer, died of a heart ailment Feb. 16 at Cokesbury Village retirement community in Hockessin, Del., where she had lived since 1988.

The death was confirmed by Donald A. Ritchie, a family friend.

Mrs. Merrill was the widow of Horace Samuel Merrill, a professor of history at the University of Maryland. They were the co-authors of the 1971 book “The Republican Command, 1897-1913.” She also helped her husband in the mentoring of graduate students. They had been married for 53 years when he died in 1996.

Marion Galbraith was born in St. Johnsbury, Vt. She was a 1942 graduate of Rollins College. That same year, she came to Washington and worked for a year as assistant to the president of American University.

Before moving to Delaware, she lived in Silver Spring.

In the 1950s, Mrs. Merrill and her husband participated in protests against racial segregation in Maryland. They participated in the 1965 Selma to Montgomery March in Alabama for voting rights, and they were active in the Giles-Johnson Defense Committee, which was formed to defend three African American men sentenced to death in Montgomery County in 1961 for the rape of a white woman. The three men were freed in a Supreme Court decision.

She had no immediate survivors.

— Bart Barnes