This dissertation examines the interaction between Franciscan missionaries and the indigenous people of California at the Franciscan missions (1769-1833). Using the framework of the seven Roman Catholic sacraments, it considers how sacramental rituals were adapted to the mission context. By focusing on religious practice, as opposed to the evaluation of religious beliefs, it seeks to problematize the notion of conversion to Christianity. Doing so also provides a way to consider the historically-overlooked agency of the Native Americans of California. This work has implications for the global, multicultural church of the present, providing historical evidence for modern theological tools such as multiple religious participation and liturgical inculturation.