This article investigates the changing construction of masculine identities among working-class males in a large Canadian factory city, Hamilton, Ontario, in the half century before the Second World War. It argues that, long before individual working men embraced the patriarchal identity of breadwinner and head of family, they had learned and practiced how to be “masculine” in family homes, schools, city streets, workplaces, and pleasure sites. The result was a complex bundle of contradictory attitudes and practices in which the processes of class, ethnic/racial, and gender formation were closely interwoven and in which the male body became a crucial vehicle for expressing gender. The article stresses that working-class masculinities were not fixed, static, or universal, but shaped in specific ways in different contexts and subject to challenges and re-negotiation over time. In the period under study here, working-class males faced new forms of institutional regulation in schools, workplaces, streets, and military trenches, the commercialization of many of their pleasures, and new independence and assertiveness in the pubic sphere among the women of their communities. Negotiating these challenges brought both continuities and significant changes in masculine identities.