Drawing on an extensive source base spanning five hundred years, from the first half of the sixteenth century to the present, this is the first comprehensive, data-driven study of both historical and modern varieties of Nahuatl, a major Indigenous language spoken in North America. Employing multidisciplinary methods and a diachronic perspective, it identifies the key social, cultural, and linguistic factors that have interacted to motivate language change and the evolution of the social and cultural ecologies of the Indigenous communities in today's multilingual and multiethnic Mexico. It provides a critical enrichment of Western theories of contact-induced language change, continuity, acculturation, and resilience, paving the way for new relational methods of studying these complex phenomena across time and space. It is essential reading for researchers in contact linguistics, historical and synchronic sociolinguistics, Hispanic and Latin American studies, and linguistic typology. This title is also available as open access on Cambridge Core.