This 10 minute clip from a BBC documentary does an excellent job of summing up the story of the Carter Family and the lasting influence they have had. I believe the title of the program was "Lost Highway".
The group shown performing live is The Whites. You have probably heard their redition of "Keep on the Sunny Side" which is on the soundtrack to "O Brother Where Art Thou".
The group who appears in the recreation of the Bristol Sessions is the cast from a musical called "Keep on the Sunny Side" which I hope to be able to see one day.
My favorite part of this clip are Carter Family home movies from what looks like the late 1950's.