All of the below historical texts are available at Archive.org American Libraries. There are certainly more 19th century tracts and pamphlets published in the same vein that have not yet been made available digitally.
Anthropological investigations on one thousand white and colored children of both sexes, the inmates of the New York juvenile asylum, with additional notes on one hundred colored children of the New York colored asylum - Hrdlicka, Ales, 1869-1943
http://www.archive.org/details/anthropologicali00hrdlrich
The colored people of Chicago : an investigation made for the Juvenile Protective Association, by A.P. Drucker, Sophia Boaz, A.L. Harris [and] Miriam Schaffner / by Louise De Koven Bowen http://www.archive.org/details/coloredpeopleofc00bowe
