Arguably the most important parallel between mass incarceration and Jim Crow is that both have served to define the meaning and significance of race in America. Indeed, a primary function of any racial caste system is to define the meaning of race in its time. Slavery defined what it meant to be black (a slave), and Jim Crow defined what it meant to be black (a second-class citizen). Today mass incarceration defines the meaning of blackness in America: black people, especially black men, are criminals. That is what it means to be black.