Drawing on the concept of a “complex humanitarian crisis,” this paper describes how outflows of migrants from Central America were transformed into such a crisis by intransigent immigration and border policies enacted in both Mexico and the United States. We describe the origins of the migration in U.S. Cold War interventions that created many thousands of displaced people fleeing violence and economic degradation in the region, leading to a sustained process of undocumented migration to the United States. Owing to rising levels of gang violence and weather events associated with climate change, the number of people seeking to escape threats in Central America has multiplied and unauthorized migration through Mexico toward the United States has increased. However, the securitization of migration in both Mexico and the United States has blocked these migrants from exercising their right to petition for asylum, creating a growing backlog of migrants who are subject to human rights violations and predations both by criminals and government authorities, leading migrants to label Mexican routes northward as a “corridor of death.” We draw on data from annual reports of Mexico's Red de Documentación de las Organizaciones Defensoras de Migrantes (Network for the Documentation of Migrant Defense Organizations) to construct a statistical profile of transit migrants and the threats they face as reported by humanitarian actors in Mexico. These reports allow us to better understand the practical realities of the “complex humanitarian crisis” facing undocumented migrants, both as unauthorized border crossers and as transit migrants moving between the southern frontiers of Mexico and the United States. Policy Recommendations Policy makers need to address: Governments must recognize that the humanitarian crisis facing migrants is not confined to border regions but unfolds at places of both origin and destination as well as within extended geographies of transit in-between. The current refugee protection regime and asylum system are ill-matched to the needs and vulnerabilities of today's migrants. In an era of rapid climate change, rising state failures, and escalating violence, people are not moving so much to advance economically as to escape a growing array of threats not covered by the 1951 Refugee Convention, which needs to be updated. Developed nations must honor rather than elide their obligations under international law to accept asylum applicants and fairly adjudicate their cases, Since a large fraction of the Central Americans arriving at the southern US border have relatives in the United States, creating a pathway to legal status for unauthorized US residents would relieve a lot of the pressure on the asylum system by enabling authorities to release applicants to the support and care of legally resident relatives rather than placing them in an overburdened detention system. Governments need to scale back the securitization and criminalization of migration, which have made human mobility an increasingly precarious and risk-filled activity that contributes to rather than forestalls the proliferation of crime and violence. Human rights and humanitarian agencies need to revisit their missions to derive new ways of working conjointly and in parallel with each other and with governments to better understand and meet the needs of migrants in the 21st century.