Evers, 37, was instrumental in desegregating the University of Mississippi and investigating the death of Emmett Till, a black 14-year-old killed for reportedly flirting with a white woman.
Carrying T-shirts that read "Jim Crow Must Go," Evers was assassinated hours after President John F. Kennedy gave a nationally televised speech in support of civil rights.
De La Beckwith was charged but set free after all-white juries twice failed to reach a verdict.
Three decades later, the state reopened the case and in 1994 a jury convicted De La Beckwith, then 73, of murder. He died in prison seven years later.