During the period between 1870 and 1910, the category of adolescence, increasingly defined the transitional stage between childhood and adulthood in the press, law, and in everyday practice. This emerging category included youths between the ages of fourteen and twenty-one as civil and penal codes recognized it as the transition from childhood to adulthood, a label that was picked up in the press, in scientific discourses, and in the courtrooms. Thus, this study addresses the following questions: What were the changes in the notion of childhood from the 1870s to the 1890s, and what did they signify to this period of economic, technological, social, and legal transformations? What were the ramifications of these cultural assumptions of childhood in civil and criminal law? What larger social forces did the rise of adolescence reflect? To what extent did the analysis of emotions in childhood and adolescence play a role in the cultural framework of positivism? This project chronicles the ascendance of the categories regarded culturally and legally as childhood and adolescence. It covers the period during the advent of the anti-colonial insurgency against Spain in Cuba and during the thirty-four–year period (1876-1910) when educators, criminologists, reporters, and parents took on these questions as age-based categories in civil and criminal law; and institutions organized around age became the norm in law and in everyday practice in Mexico. While scholarship has approached the history of childhood and youth from the prism of Mexico City, this project contends that the first war for Cuban independence (1868-1878) had cultural reverberations on the Yucatán peninsula as well as on mainland Mexico. Yucatán witnessed the arrival of educators whose experiences of war in Cuba and exile to Mexico inspired them to turn their attention to the cultivation of honor and trust in children because these emotions were considered fundamental to the proper training of young Mexican citizens. The emotional training of children viewed anger as a negative emotion while the pleasant and desirable emotions of trust and honor were particularly significant in the articulation of a uniquely Mexican emotional standard of child rearing. These ideas, which emerged in the context of Cuba’s anti-colonial insurgency in 1868 against Spain served in the Yucatán peninsula as the intellectual basis for the program of emotional education, which was central to the ideology of positivism. In the disciplines of criminology and pedagogy, the attitude toward children’s emotions degenerated to the generally negative, and the hereditary factors of working-class children informed perceptions of juvenile delinquency in the Mexican press. The press during the 1880s and 1890s generated fears about child criminality, emphasizing the emotions of envy and distrust attributed to working-class children. In the 1890s and the 1900s, newspaper chronicles of youth suicide in the press produced a cultural shift from a notion of suicide based on monomania, which affected middle-class and professional adolescents, to the concept of suicide as an expression of hereditary pathologies and moral weakness attributed to working-class youths. Violent Passions argues that the invention of adolescence as a dangerous stage of development was forged both by fear of juvenile crime and stereotypes in the press as well as by new courtship practices among adolescents. Although parents in Yucatán asserted a strong influence over their daughters’ prolonged courting phases or plazos, increasingly minors challenged parental authority by drawing on notions of autonomy, romantic love, and their own concept of innocent girlhood as well as by making accusations against fathers. The shift from supervised and prolonged courting phases to young couples’ demands for the recognition of emotional concerns in their relationships generated perceptions of juvenile delinquency in Porfirian Yucatán. Violent Passions contends that scholars should regard the emergence of the category of the adolescent as an ongoing cultural conversation concerning the role of emotions in the shaping of childhood and in the life stage of adolescence, which took hold in the early years of the Porfiriato. Although scholarship on youth in modern Mexico has focused on the formative identification of youth within the framework of institutions, namely, juvenile tribunals and universities, this project draws on the analytic construct of the life stage to trace the role of emotions from childhood to adolescence in Mexico. This dissertation considers the contingent demarcations in this period as well as the role of emotions in the meaning and process of attaining adolescence in modern Mexico.