Post 19 Nov. repeats post by Joe Offer. As someone said above, a good song regardless of who wrote it.
Merle Travis is given the credit by Encyclopedia Britannica.

Edith Fowke and Joe Glazer, "Songs of Work and Freedom," pp. 52-53, 1960, reproduce sheet music as copyright by American Music Co., 1947. Words and music are credited by Fowke and Glazer to Merle Travis. In their notes to the song is this statement:
"The key line, "I owe my soul to the company store," was a favorite expression of Travis's father who worked in the coal mines of Beech Creek, KY. Travis said: "My Dad never saw real money. He was constantly in debt to the coal company. When shopping was needed, Dad would go to a window and draw little brass tokens against his account. They could only be spent at the company store. He used to say: "I can't afford to die. I owe my soul to the company store."
"There were two coal mines in Beech Creek. One was called No. 5, the other No. 9. You were lucky if you worked in No. 5 because No. 9 had a low ceiling which made it harder to dig your daily quota of sixteen tons."

Does anyone know the source of these quotes from Travis?