Throughout its history, the United States has been structured by a racial caste system. From slavery to Jim Crow to mass incarceration, these forms of racialized social control reinvented themselves to meet the needs of the dominant social class according to the constraints of each era.
This is a pretty complicated answer with a lot of ways you can take it. I am linking here this excerpt from Michelle Alexander's amazing book, The New Jim Crow, as a resource for you to find out more depending on what you are doing as an assignment.
Hope this helps, and reach out with any questions!