The shape, function, and social meaning of the Mexican family changed alongside its relationship to the state, the Catholic Church, and popularly held beliefs and customs over the course of the 20th century. Liberal reforms of the 19th century, and in particular the Penal Code of 1871 and the Civil Code of 1884, accelerated the intentionally political function of the family, as policymakers sought to bring the domestic sphere into the service of the state. Although domestic policies aimed to wrest influence over the private sphere from the Catholic Church, both the secularizing effects and economic impact of these efforts resulted in markedly unequal gender standards. The Mexican Revolution of 1910 wrought some dramatic demographic changes that had a long-term impact on family structure, gender roles within the family, and, perhaps most significantly, the resulting revolutionary government’s conception of the role that the family unit ought to play in nationalist development projects. The post-revolutionary decades saw the reinterpretation of late-19th-century liberalizing tendencies to align the family more consciously with a vision of a modern, collectively identified economic nationalist vision of the future. Men, women, and children saw their social roles reimagined in the rhetorical ideal, even as agrarian and educational reforms revised individuals’ relationships to the labor and socializing institutions that had come to define their identities. By the 1940s, economic growth, political stability, and technological advances in medicine and healthcare all contributed to the beginning of a surge in population growth that continued until the early 1970s. Coupled with a radical shift in population density to the urban areas, these changes contributed to transformations in family residence patterns, the division of labor, and the role of children and young people. But events in the 1970s conspired to bring a radical end to the high birth rate. These included the conscious domestic-policy reform of the Luís Echeverría administration (1970–1976); the availability of contraception and its tacit approval by the Mexican Catholic Church; the transnational feminist movement, culminating in the 1975 meeting in Mexico City of the United Nations’ Conference on Women to commemorate International Women’s Year; and, not least of these, preventive measures taken by citizens themselves to reduce the strain on the family unit. By the end of the 20th century and the beginning of the 21st, transnational migrations and remittances came to define an increasing percentage of families and kinship structures.