I was reading some notes put out be Stefan Grossman's Guitar Workshop that gave some background on the song as well as Merle's other mining songs. In the early 1950's Merle's popularity as a country singer was waning—though not his reputation as a guitarist—when someone suggested he make an album of folk songs. Merle didn't want to do that because "all the folk songs had already been recorded." "Well then write some." was the reply. The result included both "Dark As A Dungeon" and "Sixteen Tons."

      - Mark