This is what Albert E. Brumley said about his composition:
"I was picking cotton on my father's farm and was humming the old ballad ["The Prisoners Song"] that went like this: "If I had the wings of an angel, over these prison walls I would fly" and suddenly it dawned on me that I could use this plot for a gospel-type song.
About three years later, I finally developed the plot, titled it "I'll Fly Away," and it was published in 1932 [in "Wonderful Message," Hartford Music Co,]
"Those familiar with the song will note that I paraphrased one line of the old ballad to read "Like a bird from prison bars have [has] flown." When I wrote it, I had no idea that it would become so universally popular."
From letter to Dorothy Horstman from Brumley, Jan. 10, 1973; reprinted Dorothy Horstman, "Sing Your Heart Out, Country Boy," 1976, p. 51."

From Bob Dylan Roots

"The Prisoner's Song," as generally known, was written by Robert Massey and copyright by Guy Massey, 1924, Shapiro, Bernstein & Co. Inc. (also from Bob Dylan Roots)