During the Civil Rights era, Clark was a special assistant to Medgar Evers, field secretary for the NAACP. Clark was the founder and first president of the North Jackson NAACP Youth Council, under the guidance of Medgar Evers and John Salter. In 1962 Clark resigned from the NAACP and joined the Mississippi Student Nonviolent Coordinating Committee to do voter registration work. In the 1990s Clark was a professor at the University of Albany. She was co-chair of the New York delegation to the Green Party of the United States presidential nominating convention, where Cynthia McKinney was nominated as the Green Party Presidential candidate. Clark is currently working on writing, activism and advocacy about Haiti.