It started with the searing sound of a slide careening up the neck of an electric guitar. In 1970, twenty-three-year-old Bruce Iglauer walked into Florence's Lounge, in the heart of Chicago's South Side, and was overwhelmed by the joyous, raw Chicago blues of Hound Dog Taylor and the HouseRockers. A year later, Iglauer produced Hound Dog's debut album in eight hours and pressed a thousand copies, the most he could afford. From that one album grew...