The United States prison population has grown seven-fold over the past 35 years. This dissertation looks at the impact this growth in incarceration has on crime rates and seeks to understand why this drastic change in public policy happened. Simultaneity between prison populations and crime rates makes it difficult to isolate the causal effect of changes in prison populations on crime. This dissertation uses marijuana and cocaine mandatory minimum sentencing to break that simultaneity. Using panel data for 50 states over 40 years, this dissertation finds that the marginal addition of a prisoner results in a higher, not lower, crime rate. Specifically, a 1 percent increase in the prison population results in a 0.28 percent increase in the violent crime rate and a 0.17 percent increase in the property crime rate. This counterintuitive result suggests that incarceration, already high in the U.S., may have now begun to achieve negative returns in reducing crime. As such it supports the work of a number of scholars (Western 2006, Clear 2003) who have suggested that incarceration may have begun to have a positive effect on crime because of a host of factors. Most of the empirical work on the question is undertaken at an aggregate level (county, state, or national data). Yet, criminologists (Sampson et al. 2002, Spelman 2005 and Clear 1996, 2007) have long argued that the complex intertwining of crime and punishment is best understood at the neighborhood level, where the impacts of incarceration on social relationships are most closely felt. This dissertation examines the question using a panel of neighborhoods in Tallahassee, Florida for the period 1995 to 2002. I find evidence to support the contention that the high levels of prison admissions and prison cycling (admissions plus releases) is associated with increasing crime rates in disadvantaged neighborhoods. This effect is not found in other neighborhoods. Looking more closely at the issues of race and class, I find that while marginalized neighborhoods experience slightly higher crime rates, they are faced with much higher incarceration rates. In Black neighborhoods in particular, prison admissions are an order of magnitude higher in comparison with non-Black neighborhoods even though underlying crime rates are not very different. If incarceration does not lower crime, then why did prison populations multiply seven-fold? This dissertation argues that mass incarceration is a central institution in the neoliberal social structures of accumulation. Mass incarceration as an institution plays a critical but underappreciated role in channeling class conflict in the neoliberal social structures of accumulation (SSA). Neoliberalism has produced a significant section of the working class who are largely excluded from the formal labor market, for whom the threat of unemployment is not a sufficient disciplining mechanism. At the same time, it has undermined the welfare systems that had managed such populations in earlier periods. Finally, the racial hierarchy essential to capitalist hegemony in the United States was threatened with collapse with the end of Jim Crow laws. This dissertation argues that mass incarceration has played an essential role in overcoming these barriers to stable capitalist accumulation under neoliberalism.