In the early 1960s in the US there was a good deal of interest in authentic American folk music, the so-called "folk boom." Some of the people who were in that scene developed an appreciation for old-time blues recordings made in the late 1920s and early 1930s. Very little was known about these recording artists and all that remained, apparently, were a few hard-to-find 78 rpm records and some old publicity photos. It occurred to a few blues enthusiasts that perhaps some of the musicians who had made the records might still be alive, so they set about trying to find them.
In fact, many blues musicians from that time and place (primarily Mississippi and Texas) were already gone. The Depression had wiped out the small recording companies that had recorded the artists, tastes in music had changed, and nearly all of the old time blues artists had died or otherwise faded into obscurity. A few, however, remained, and there are several dramatic stories of how some of the musicians were rediscovered.
For blues fans it was like travelling to London to find a group of theater actors from the Elizabethan era still performing plays by Shakespeare. The musicians were of a completely different place and time, playing in a unique, emotional style that had been lost for decades. A few, like Skip James, Son House, Mississippi John Hurt, and Bukka White, enjoyed a few short years of popularity in the mid 1960s as they played the college music and folk festival circuit and re-recorded some of their earlier songs.
Here is Skip James singing "Crow Jane" and "Devil got my Woman." James had lost a little bit of his facility with the guitar and vocal power when these movies were taken, but we're fortunate to have anything at all. It's hard to find anything more emotionally powerful than Son House singing "Death Letter." It's possible to find some video of John Hurt, Mance Lipscomb, and Lightnin' Hopkins as well. Give a listen.