This dissertation examines the history of relations between the police and the broader population in Mexico City in the period c.1870-1950. Against interpreting policing as a state-centric disciplinary project, it traces how the negotiation of police power became crucial to the informal ordering of the city in multiple registers. From the late nineteenth century onwards, the organization of public order in Mexico City underwent tremendous changes, as authorities expanded the reach of regulations and modernized the police force. These developments dramatically changed the making of public order and the relationship between citizenship and the ordering of the city. In practice, police authority was negotiated by various actors—city officials, the capital’s residents, and police themselves—on uneven terrain that shifted with changing political, social, and institutional contexts, generating regularized but informal forms of order driven by extralegal power, patron-client relationships, and the selective application of law. Using court records, administrative files, and newspapers, this dissertation examines how city residents sought to strategically employ or contest police power and criminal law, as well as tracing how police working conditions and the disjuncture between law and material conditions fostered the negotiation of regulations on public space. It further shows how these practices changed over time, especially owing to institutional changes in the police, including professionalization, specialization, and the development of private and semi-private police organizations. The negotiation of policing simultaneously allowed many city residents the chance to defend their livelihoods and sociabilities, while reinforcing their unequal and contingent integration into the city, their limited access to citizenship rights, and their vulnerability to violence. By focusing on questions of discretion, violence, and extralegal uses of police power, this dissertation highlights their centrality to the construction and maintenance of informal, negotiated means of ordering the city, and in doing so, sheds light on citizenship and its limits in Mexico City in the era.