Mapping the KKK: An animated, online map shows for the first time just how the Ku Klux Klan spread rapidly to all 50 states between 1915 and 1940. John Kneebone says the KKK was far more mainstream than most people realize, with membership of between 2 million and 8 million people. Plus: Revolution has been one of the most important drivers of human activity since its emergence in modern form in the 18th century. In his new book, Jack Censer traces the evolution of revolutionary ideas--from the American and French revolutionaries to leaders of the Arab Spring. And later in the show, a profile of Ken Rutherford who co-founded the Landmine Survivors Network. Produced by Lilia Fuquen.