My dissertation will examine how the informal institutions that sustain undocumented migration adapt to changes in border policing, tracing developments from villages in El Salvador into Guatemala and Mexico and up through the United States. In particular, I ask whether a relationship exists between immigration enforcement and institutionalized practices of criminal violence against undocumented migrants during their journey. This criminal violence includes kidnappings, extortion, robberies and rapes committed by predators that stalk illegal routes, as well as some violence by guides themselves. I conceptualize migratory routes as spatially bounded packages of sustained human practices. To understand how violent practices become embedded in these routes, I examine the role of information and imagination in migrant decisions and human smuggling markets. This examination of migrant decisions and their informal institutional context provides insights into transnational economic processes that challenge state capacity to control territory. As cargo with a voice, the stories of migrants provide a window into the causal mechanisms that underlie the global illegal economy. With their voices, I hope to highlight the human consequences of the failure of immigration policing. Working at the interstices of political science and anthropology, I have developed an innovative research strategy to investigate how migrants learn about and respond to changes in the policing environment, and in particular how the market for paid guides (called coyotes) functions. Following a year of ethnography in villages in El Salvador, I will follow the paths taken by migrants through Catholic missions in Guatemala and Mexico as part of an eclectic research design combining a rational decision making framework with rich ethnographic fieldwork.