The invention of employment law in the nineteenth century was no simple transition from servitude to wage work. Instead, lawyers created the category of employment by remaking earlier legal understandings of all labor forms through an awesome instrument of power: legal writing. In 1800, only a few imported, expensive British lawbooks were available in the United States. A new generation of legal writers reworked these texts for to the republic, aiming, at the same time to extend the rules of the commercial world of mercantile transatlantic trade into small-town transactions and middle-class lives. They marketed their products to lawyers and justices of the peace, arguing that technical legal rules should apply to ordinary disputes as well as high-stakes commercial matters. Their audience agreed, snapping up legal texts and increasingly citing them in court. These lawbooks produced the changes, however, that they purported merely to reflect. In the preceding century, legal and social thought had linked many kinds of work, from entrepreneurship to housework to slavery, even as the conditions of these labor forms differed. Early republic lawyers broke apart this spectrum of labor, developing new concepts in employment law, contract, family law, property, and business organization to regulate and distinguish between once-connected kinds of work. This dissertation resurrects a world of American labor where core ideas that we take for granted—like the separation of labor and capital—were not yet obvious. It tells unfamiliar stories, such as a self-employed expert glasscutter whose case became key precedent in master-servant law, or a husband who argued he was legally his wife’s journeyman. Finally, it shows how America’s redefinition of work was fought not merely in incipient factories, but on the battlefield of legal knowledge. Legal treatises created new norms through writers’ often invisible work of classifying and describing precedents and labor. Through legal writing, lawyers defined and buttressed an emerging economic order, one conducive to the long-term investment and credit structures, yet also determinative of the unequal forms of labor in the modern economy.