Radical changes in crime control and sentencing policies led to an unprecedented buildup of the United States prison population over the last thirty years. n1 By the end of 2002, the number of inmates in the nation's jails and prisons exceeded two million. n2 Today's imprisonment rate is five times as high as in 1972 and surpasses that of all other nations. n3 The sheer scale and acceleration of U.S. prison growth has no parallel in western societies. As David Garland put it, "This is an unprecedented event in the history of the USA and, more generally, in the history of liberal democracy." n4

The extraordinary prison expansion involved young black men in grossly disproportionate numbers. Achieving another historic record, most of the people sentenced to time in prison today are black. On any given day, nearly one-third of black men in their twenties are under the supervision of the criminal justice system - either behind bars, on probation, or on parole. n5 The gap between black and white incarceration rates, moreover, has deepened along with rising inmate numbers. n6 African Americans experience a uniquely  [*1273]  astronomical rate of imprisonment, and the social effects of imprisonment are concentrated in their communities. Thus, the transformation of prison policy at the turn of the twenty-first century is most accurately characterized as the mass incarceration of African Americans. n7

The mass incarceration of African Americans coincides with a new era in criminal justice research. Social scientists are increasingly applying empirical methods to understand the impact of crime control policies and to supply data to judges, legislators, and policymakers. n8 The distinctive features of African American mass incarceration have generated a new research agenda that reframes the typical questions asked about the racial disparity in imprisonment and that better measures the costs and benefits of prison policy. The new research also puts in striking relief the question of the morality of confining so many American citizens.

In the rest of this Introduction, I describe the distinctive features of both African American mass incarceration and the new direction in prison research examining this phenomenon. I also discuss how these empirical studies reframe the issue of racial discrimination in the criminal justice system. Part I identifies three theories that explain the social mechanisms through which mass incarceration inflicts community-level harms. Part II argues that mounting evidence of mass imprisonment's damage to African American communities should change the outcome of dominant deliberations about the moral justifications for current penal approaches to punishment. This evidence demolishes utilitarian claims that high incarceration rates uniformly benefit black communities and reveals, to the contrary, how they entrench black communities' political subordination. I conclude, therefore, that the mass incarceration of African Americans is not only morally unjustifiable, but morally repugnant.