From late 1964 to June 1965, Harriet worked with the Southern Christian Leadership Conference in Alabama. She first worked in Gadsden with a black organizer, Ben Luchion. Then, following orders from SCLC leaders, Harriet returned to Selma, teaching reading and other skills to local people from January to June 1965. Later, Harriet worked on a Southern Conference Educational Fund project in New Orleans. Harriet also served as a member of the board of directors of the Veterans of the Mississippi Civil Rights Movement, Inc.
In her later years, she returned to the South as much as possible and remained involved in local political issues. She worked as a historian and chronicler of the movement with a number of organizations and institutions, including NYU's Tamiment Library. Her most recent activities included work at WBAI, New York's progressive radio station.