One of the major purposes of the humanities is to expose students to new points of view, especially the views of minorities and other disadvantaged groups whose voices are often neglected. The Civil War Era is a particularly useful period for such considerations, as it prominently featured racial division that continue today.
The same companies that house prisoners are also paid by the government to house immigrants, creating a problem that sits at the intersection of race and capitalism. The logic behind this is simple. Private companies exist to make money. When you operate a prison, the best way to make money is to make sure that the prison is full.