Jewish involvement in the civil rights struggle also went deep. It is estimated that thousands of Jewish students made their way to the South during the 1960s, joining efforts being coordinated by a variety of organizations to arrange sit-ins and marches to desegregate transportation and schools and to register voters. One-third to one-half of the Freedom Riders in the summer of 1961 were Jewish and a similar percentage of Jews took part in the Mississippi Freedom Summer in 1964 (during which Goodman, Scherner, and Chaney were murdered). Harder to measure, but clearly affecting thousands of more Jews growing up in this era, was the widespread sympathy Jews felt for the civil rights struggle. Rabbis preached about civil rights from their pulpits. Jewish periodicals carried articles about the justice of the cause. Many of the activists interviewed for this book trace their earliest feelings for social justice to hearing their parents talk about Martin Luther King Jr., and the movement for civil rights as a moral calling. In 1963, Rabbi Joachim Prinz, the president of the American Jewish Congress and a refugee from Nazi Germany, was one of the speakers who addressed 250,000 people at the March on Washington. It was the same stage from which, minutes later, Martin Luther King Jr. would deliver his historic "I Have A Dream" speech. To the extent that one of the great accomplishments of the civil rights movement was making de facto discrimination illegal, the organized Jewish community threw all of its political muscle behind the passage of the era's two most important pieces of civil rights legislation- the Civil Rights Act of 1964 and the Voting Rights Act of 1965.