This essay recovers the power of English grammar for ordinary Americans in the early nineteenth century, when hundreds of grammars were composed and printed. Between their cheap covers, these books contained the arresting possibilities of what Raymond Williams called the “third revolution,” a cultural transformation that was intimately tied to profound political and economic changes in the eighteenth and nineteenth centuries. The power of English grammar lay in its ability to enable rail-splitters, weavers, ragpickers, and former slaves everywhere from the Blue Ridge to Boston to begin to speak and write for themselves. By unlocking its mysteries, even the self-taught believed they might “converse with a thousand worlds.” The story of grammar’s popularity intersects several fields—the history of the book and reading, the history of education, rhetoric, and social and cultural history. Historians of curriculum and rhetoric have long highlighted shifts in language usage in the nineteenth century, but their insights have not been much noticed by social historians. Those few social historians attentive to language, meanwhile, have focused on how the language of social class changed over time. This essay takes a different approach. It examines how and why ordinary people studied the English language itself. It plunges beneath the surface of “education” and “literacy”—routinely invoked as agents of social change in early America—to ask why ordinary people pursued learning and how they used their books. It shifts attention away from the statistical measures of illiteracy to consider the qualitative meanings of knowledge in everyday life.