This essay proposes a feminist research agenda on the history of women teachers' experiences in the latter stages of their career and life. Drawing on extant histories of white women elementary and secondary teachers in the largely Anglo, western world (centred on the United States, Canada, England, Australia and Ireland), the essay explores the concept of age as a category of analysis, particularly for historians of women, by identifying three ways in which the ageing of women teachers is historically significant: the persistence of cultural stereotypes against older women teachers over time; the historical pattern of older women teachers' political activism; and historical aspects of ageing women teachers' sense of professional and subjective experience of their work. By noting the invisibility of age in the current historiography of women teachers, the essay proposes that historians of education begin to see age as a category of analysis.