Identity is a dynamic. It changes across time and contexts. This presents a methodological challenge because established methods (interviews, surveys, experiments) are not ideal for tracking people across time and as they move between contexts. Increasingly, however, people leave textual traces of their identity in diaries and letters, that document changing identities across time and place. Since ancient Greece, autobiographical writings (letters, confessionals, diaries) have been a literary technique for people to explore and display their identities; subsequently, such self-writings offer researchers precious access to the situated and dynamic identities of others. We approach identity from a developmental, sociocultural, and dialogical perspective, and we thus consider diaries, letters, and blogs as providing a precious window on the development of identity. Specifically, we conceptualize self-writings as simultaneously an externalization of a person’s experience and a reflection upon her experience, addressed to real or imaginary audiences. Based on a ideographic study of diaries, we will show both how the development of subjective identity can be traced through time, as the diarist moves through real and imaginary spaces. Such analysis, we argue, demands both a careful, theoretically informed examination of form and content of texts, and the reconstitution of the environment in which these texts have been produced. Finally, we discuss new directions for the study of identity through increasingly diverse forms self-writing, such as online diaries, emails, text messages, letters, and social media.