This thesis examines the work of the Health League of Canada, a Toronto-based voluntary public health organization, from 1935 to 1980. Using archival sources, it explores the efforts of the Health League’s Child and Maternal Health, National Immunization Week, National Health Week, Industrial Health, and Gerontology committees. It argues that the Health League undertook its educational campaigns not only to promote preventive health and physical wellbeing, but in doing so to improve the moral calibre and economic prosperity of the Canadian nation. The Health League emphasized individual responsibility, and urged Canadians to actively monitor their health behaviour, portraying it as a fundamental part of active citizenship. Despite shifting public health approaches over the course of the twentieth century, marked by increasing specialization and reliance upon therapeutic developments, the Health League remained committed to its educational model and emphasis upon individual preventive health and civic responsibility. It therefore provides an opportunity to consider the work of an influential and long-lasting public health organization over the course of the twentieth century.