The Anchor Line verse

De City of Cairo's a mighty big gun,
But lemmee tell you whut de Monroe done;
She lef' Baton Rough at haff pass one
An' git ter Vicksburg at de settin' er de sun.

is related to the railroad song "Dummy Line" which includes the following verses:

Some folks say that the Dummy don't run
But come let me tell you what the Dummy done
She left St. Louis at half past one
And she rolled into Memphis 'for the settin' of sun.

and

Some folks say that the Dummy don't run
But come let me tell you what the Dummy done
She left St. Louis at half past two
And I walked into Memphis 'fore the Dummy came through.

Be interesting to know which came first.