The recording from which, according to Norm Cohen, Leadbelly most probably learned the song was made by John Lomax from a group of convicts at Cummins Farm in Gould, Arkansas, in 1934:

ROCK ISLAND LINE

I says the Rock Island Line (lead)
Is a mighty good road (all)
I says the Rock Island Line (lead)
Is the road to ride (all)
I says the Rock Island Line (lead)
Is a mighty good road (all)
If you want to ride, you gotta ride it like you're flyin'(all)
Buy your ticket at the station on the Rock Island Line (all)

Well, Jesus died to save me in all of my sin (lead)
Well-a, glory to God, we goin' to meet Him again (all)

I says ...

Well, the train left Memphis at half pas' nine (lead)
Well, it made it back to Little Rock at eight forty-nine (all)

I says ...

Well, Jesus died to save me in all of my sin (lead)
Well-a glory to God, we goin' to meet Him again (all)

I says ...

Source: Various Artists 'Train 45: Railroad Songs of the Early 1900s' Rounder CD 1143.