Martin Luther King Jr. encourages freedom riders as they board a bus for Jackson, Miss., 1961. (Paul SchutzerTime & Life Pictures/Getty Images)
White segregationists hurl stones at a bus carrying freedom riders in Mississippi. (Paul SchutzerTime & Life Pictures/Getty Images)
Freedom riders on a bus in the Deep South. (Paul SchutzerTime & Life Pictures/Getty Images)
Julia Aaron and David Dennis, along with 25 other freedom riders and several members of the National Guard, travel from Montgomery, Ala., to Jackson, Miss. (Paul SchutzerTime & Life Pictures/Getty Images)
Just shy of the Mississippi-Alabama border, members of the Alabama National Guard surround a bus carrying freedom riders. (Paul SchutzerTime & Life Pictures/Getty Images)