An article in the "Literary Digest," reproduced in the "African Methodist Episcopal Church Review, vol. 15 #3, 1899, mentions several black composers of the 19th c. A few quotes:
"The Negro is the coming musician of the United States. So thinks John Edward Bruce.... in the Boston Evening Transcript in which he tells of some of the songs written by negroes.
The first one he mentions is "Listen to the Mocking-Bird, by George Milburn, a street minstrel, who, being too poor to publish it, sold it to Winner, who has generally received credit for it."

On The Baggage-Coach Ahead," by Gussie L. Davis-
"He is the young negro song-writer who won the second prize recently given by the New York World for the best song written by an American song-writer. He was really entitled to first prize, but the judges took into account the fact that he is a negro and gave him second prize.... More than 500,000 of his best songs have been sold within the past dozen years, and there is not a city in the United States where they are not sung or played by the bands."

American Memory. Enter The baggage-Coach Ahead into the Search blank.
Baggage-Car
A copy of the sheet music also at this website.