Contact, Structure, and Change addresses the classic problem of how and why languages change over time through the lens of two uniquely productive and challenging perspectives: the study of language contact and the study of Indigenous American languages. Each chapter in the volume draws from a distinct theoretical positioning, ranging from documentation and description, to theoretical syntax, to creole languages and sociolinguistics. This volume acts as a Festschrift honoring Sarah G. Thomason, a long-time professor at the University of Michigan, whose career spans the disciplines of historical linguistics, contact linguistics, and Native American studies. This conversation among distinguished scholars who have been influenced by Thomason extends and in some cases refracts the questions her work addresses through a collection of studies that speak to the enduring puzzles of language change.