The Republican convention in Tampa, Fla., touches on a date that has marked the depths and the heights of the African-American experience in this country. On Aug. 28, 1955, Emmett Louis Till, a 14-year-old African American visiting his relatives, was brutally murdered in Mississippi for whistling at a white woman. His funeral — with an open casket that displayed the barbarity of the attack on him — attracted tens of thousands in Chicago and helped spark the growth of the civil rights movement. On Aug. 28, 1963, the Rev. Martin Luther King Jr. helped lead the March on Washington, where …
