Here's the original, apparently. It's only slightly different from the one in DT.

From The University of South Carolina Sheet Music Collection:

THERE'S A LONG, LONG TRAIL
Words, Stoddard King. Music, Zo Elliott. 1917.

1. Nights are growing very lonely.
Days are very long.
I'm a-growing weary only
List'ning for your song.
Old remembrances are thronging
Through my memory,
Till it seems the world is full of dreams
Just to call you back to me.

CHORUS: There's a long, long trail a-winding
Into the land of my dreams,
Where the nightingales are singing
And a white moon beams.
There's a long, long night of waiting
Until my dreams all come true,
Till the day when I'll be going down
That long, long trail with you.

2. All night long, I hear you calling,
Calling sweet and low.
Seem to hear your footsteps falling
Ev'rywhere I go.
Though the road between us stretches
Many a weary mile,
I forget that you're not with me yet
When I think I see you smile.