The legal construction of public space and the physical character of vernacular architecture were fundamentally interrelated in the nineteenth-century United States. The hotel appeared as a distinct architectural form at the end of the eighteenth-century, and over the course of the following century supplanted the tavern as the standard form of American public accommodation. The innovative physical and social character of hotel space fostered two distinct legal transformations. First, it caused the right to enter and make use of public houses to be broadened to apply not only to travelers who took rooms, but also to ant person who wished to enter, whether to take a room, visit a guest, or simply solicit the business of those inside. This broad right of access to public accommodations was established over the wishes of proprietors to preserve their authority, which in the days of the local tavern had not been seriously questioned. Second, legal regimes which applied to specific kinds of spaces were overflowing their boundaries and influencing the legal construction of different kinds of space. The new order of innkeeper law, on the basis of its status as part of the law of common carriers, came to be applied to restaurants, theaters, trolleys, bars, and railway cars. An examination of the development of the common law of innkeepers and public accommodation thus demonstrates how changes in the built environment altered how American judges interpreted the law; it also demonstrates the determinative force of legal categories in the definition of public space.