The song is listed often as a favorite during the Civil War. Its true origin seems to be unknown.
Kendall Morse (cd through Camsco) arranged a version of it. A hit for the Sons of the Pioneers, among others.

The song is in Brown's North Carolina Folklore, No. 711. I only have volume 5, The Music, but two stanzas are given with the music.

MY PRETTY QUADROON

Oh, who was as happy as I?
She'd a brow like the blossoming pea-
And the light of her violet blue eyes
Never shone on a darkey like me.

Cho.
Oh my pretty quadroon
The flower that faded so soon,
This heart, like the strings on my banjo
Am broke for my pretty quadroon.

Her face was exceedingly fair,
She'd a cheek like the wild rose of June-
And the ringlets of her dark glossy hair
Was the pride of my pretty quadroon.

The music of the chorus differs a little from that normally heard. In the third line, heart and strings are equally low notes.
The song is strangely absent from Vance Randolph, Ozark Folksongs.