Research in mathematics education has described learning and identity development as dynamic, negotiated, and cultural. However, disciplined ways of engaging in school mathematics remain most valued, resulting in positioning only some learners as successful. Research that investigates mathematics learning and identity has predominantly occurred in classrooms or takes up non-school sites as comparisons to classroom settings. Additionally, there is a significant body of literature which documents the differential learning experiences of historically marginalized students based on race, gender, and sexual orientation. These studies highlight how racist, sexist, and homophobic institutions structure the processes of mathematical socialization, but they conceptualize learning as bounded, vertical trajectories toward disciplinarily defined learning goals. Left unproblematized, the singular dimension of learning continues to obscure students' repertoires of practice and the ways these repertoires are embedded in their identities as simultaneously contextually-specific and historically rooted performances. Taking a sociocultural perspective on learning and identity as dynamic processes, developed across settings and through interactions, this study explores how youth's learning and identities are co-constructed through everyday practices and interactions. A multi-sited, person- centered approach is used to bring the relationships between sites into analytical focus to examine how learners coordinate places and experiences. Attending to these connections supports challenging deficit frames of youths' lifeworlds and marginalized identities as obstacles to learning. The initial site is an after-school documentary workshop. From there, observations extend outward into the lifeworlds of two case study youth. Drawing on video and audio recordings of interactions, analysis traces the development of representational tools to understand the ways in which youths' forms of participation shaped their identity enactments. Findings reveal the interconnectedness of identity enactment and learning. Implications call educators and researchers to (re)imagine learning and becoming as co-constructed, ongoing, historical, personal, and multi-sited. Implications speak to the need for an ontological shift - (re)conceptualizing the classroom as an unbounded ecological web - and for further study of the educational experiences of students with historically marginalized identities. This shift could generate a more robust way of describing mathematical identities, which in turn may produce more expansive, and thus more equitable, views of mathematics. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]