This corpus study traces the history of MILLION in English. It focuses on the shift in word class/function from noun/noun-phrase head (three millions of dollars) to determinative/determiner (three million dollars). A chapter on morphosyntax/semantics probes the natural word class and function of number words and their historical categorization. A composite international diachronic corpus is used to map a broad taxonomy of MILLION phrases, and very-large-scale digital American and British newspaper archives are used to show when and where the syntactic shift took place. The tens of billions of datable words in these sources yield such robust results that key phases in the shift can be traced in unprecedented detail, uncovering surprising patterns in American/British differences and an avoidance strategy in the use of numeral and number-word expressions. Retarding and accelerating factors are treated in separate chapters.