After 1945, artists like Muddy Waters, Howlin' Wolf and John Lee Hooker rooted the blues firmly in the city, where it contributed to the musical desegregation of America by spawning rock 'n' roll. As the blues conquered the world and the music moved from black to white audiences, arguments developed about what was the real authentic blues. Robert Johnson returned from the dead to sell more records than any other blues artist. By the 21st century, the blues not only retained the earthiness of its roots but was also being celebrated in the White House. With contributions from Keith Richards, Bonnie Raitt, Seasick Steve and Buddy Guy.