Aha! It was Wyoming. In his introduction to the Liner notes on the Harry Jackson album, my dear departed friend and mentor Kenny Goldstein wrote that Harry met Ed Marshbank while he was a teenager working on Wyoming ranches, including the Whitt ranch on Rawhide Creek and the River Ranch on Wood River. On both these ranches, he apparently worked with Marshbank building corrals, and learned many songs from him, including "Clayton Boone."

You should be able to download those complete liner notes as a pdf, here

Best of luck!