Older people became a highly visible force in the American politics of the 1930s. The Townsend organisation mobilised one tenth of the U.S. elderly population prior to their direct representation in the polity as an interest group. This article utilises several theoretical social movement models to analyse how and why mobilisation occurred. It demonstrates that many factors, including phenomena associated with the social dimension of age, influenced the mechanisms of mobilisation and the movement's shape. Characteristics of this cohort of older people, including its size, life expectancy, spatial distribution, shared traditions, and symbolic frameworks were conducive to club formation and mobilisation. The period event of the Depression also triggered collective action, by exacerbating trends of changing old-age institutional supports. But the organisation expanded most where it channelled inducements to participants and evoked the cohorts' symbolic frameworks and ideals. Mobilisation also occurred within a political environment, the national stage of U.S. politics, where non-represented interest groups (such as elderly people) find it difficult to receive benefits.