The Newberry Library in Chicago has the sheet music, described as follows:

Author: Dodge, Mary.
Title: MY PRETTY QUADROON words & melody by Mrs. Mary Dodge arranged by T. Martin Towne. Of the Continental Vocalists.
Published: Chicago : Published by H.M. Higgins 117 Randolph St. Entd according to act of Congress AD 1863 by H.M. Higgins in the clerks office of the Dist. Court of the Northn Dist of Ill., [1863]
Physical Description: 5 p. 33 cm.
Subject (LCSH): Songs (Medium voice) with piano.
Subject (Other): Illinois Chicago 1863 Imprints.
Other Name: Higgins, H. M. (Hiram M.), 1820-1897, publisher.
Notes: Plate markings (p. 3-5): My pretty quadroon.
For solo voice, chorus (SATB) and piano.