Written by Junior Parker and first recorded by Little Junior’s Blue Flames (1953).
Hit version (as a B-side) by Elvis Presley (C&W #10 1955).
Also recorded by Junior Wells (1967), The Band (1973), Neil Young (1983).
From the wiki: “The original recording of ‘Mystery Train’ was written by Herman ‘Junior’ Parker and recorded by him (billed as Little Junior’s Blue Flames) at Sun Studios in 1953. And, of the many groundbreaking songs recorded by Elvis Presley during his storied career, ‘Mystery Train’ has come to be regarded key to understanding his unique place in the Rock and Roll canon, with Sam Phillips, as producer of both the Parker and Presley recordings, serving as mid-wife.