Picking cotton at the Louisiana State Penitentiary in Angola (one of the few places in the U.S. where cotton is still picked by hand), these convicts evoke blues music's ancestry. The roots of the blues are in the cotton fields of the South where slaves would sing to keep the blue devils at bay. The cadence of those field songs later came to shape the musical structure of today's blues.

(Text adapted from and photograph shot on assignment for, but not published in, "Traveling the Blues Highway," April 1999, National Geographic magazine)