Miriam Schaffner 
The Colored People of Chicago / An Investigation Made for the Juvenile Protective Association [PDF ebook] 

In the course of an investigation recently made by the Juvenile Protective Association of Chicago upon the conditions of boys in the County Jail, the Association was much startled by the disproportionate number of colored boys and young men; for although the colored people of Chicago approximate 1/40 of the entire population, 1/8 of the boys and young men and nearly 1/3 of the girls and young women who had been confined in the jail during the year were negroes.