This is what Wallace Stegner has to say, discussing his novel, The Preacher and the Slave

"later, while I was working on the novel, I discovered Mac McClintock, who wrote 'The Bum Song,' 'Hallelujia, I'm a Bum,' and others. He said he wrote "The Big Rock Candy Mountain," too, and Victor at least paid him royalties as author. Actually, I think "The Big Rock Candy Mountain" was written by T-Bone Slim, or some other nameless balladeer, a long time before McClintock came along. He may have added two or three verses. In any case, he recorded all those for the first time, and McClintock had an even closer connection to the Joe Hill legend. He sang Joe Hill's 'Pie in the Sky' song on Burnside Street in Portland, reading it off an envelope or laundry tag Joe Hill had handed him. That was the first time 'Pie in the Sky' was sung on the street...."

Conversations with Wallace Stegner (University of Utah Press, 1990),p. 70.