This book investigates -s marking in English verbs, specifically its manifestations in main verbs, in the past tense of BE, and in existential constructions. It embraces the many ways in which -s marking varies across the English speaking world, and considers both how it arose in these places historically and the ways in which it has since developed. The authors propose a story which holistically accounts for these different manifestations of -s, drawing upon evidence from a wide range of subdisciplines in linguistics, including sociolinguistics, generative syntax, historical linguistics, dialectology, and discourse-pragmatics. This book will be of particular interest to students and scholars in these and related fields.