The original title applied to "Goodbye to the Plains" is "The Dying Cowboy of Rim Rock Ranch."

Austin E and Alta S. Fife had this to say about it-
"This "Dying Cowboy" is a folkish bending of cowboy imagery to transcendental notions basic to the Christian faith. Life and salvation are for man what the roundup and trail drive are for the dogies. Note how the realistic range images of the first text get molded, in the second one, into the transcendental images of life and death. (Melody and Text A: Library of Congress #856B2, recorded by John A Lomax. Text B: Library of Congress, collected by John A. Lomax."
The Carter version changes the chorus (with changes) to last verse, and uses little of the Lomax texts except the first line. The religiosity angle survives, but little else is the same.

Probably an early (1920s) product of someone in the fledgling "cowboy church" which holds informal services at rodeos and the like.