"This dissertation examines the multiple and complex ways in which residential space defines, is defined by, affects, is affected by, and interacts with community social life. I use the case of mano dura contra el crimen [hard hand against crime] policies to investigate how changes to the built environment affect communities' identities and segregation. The policies of mano dura, implemented in Puerto Rico in the decade of the 1990's, consisted of a range of architectural, urban design, and programmatic interventions implemented throughout the island's public housing sites with the purpose of eradicating crime. In the dissertation, I utilize a multi-method approach employing historical, quantitative, and qualitative methodologies to understand how the changing built environment affected crime, social identity, and social interaction. Organized in three sections, in the first part of the dissertation I rely on qualitative interviews and archival data to trace the development of the mano dura policies and expose the underlying logics of the policy and its interventions. In the second part of the dissertation, I utilize geographic data to conduct an impact evaluation that assesses whether the public housing policies resulted in a reduction in crime over a six-year period. In the third section, I used qualitative methods such as focus group interviews with public and private housing residents, individual interviews with administrators and officials, and systematic observation of the built environment to understand how the changing built environment affected the social dynamics of the communities. The dissertation examines the costs of fighting crime through built environmental interventions. It demonstrates how the built environment, and residential space in particular, conspire with communities' social dynamics and perceptions through a complex process that results in increased segregation and structured and edified social labeling. In addition, the built environment impacts the access that individuals in communities have to social interactions within and across communities through different methods that include limiting physical mobility within and across communities and impacting cognitive understandings or symbolic branding of space. "