One of the most enduring questions about private property is why it develops. Strongly influenced by a short article by economist Harold Demsetz, property scholars recently have analyzed the evolution of private property in economic and social terms, as a response to factors such as changes in relative prices, measurement costs, and the size and heterogeneity of user groups. This Article argues that Demsetzian-inspired accounts of the evolution of private property tend to neglect the role of the state in property rights formation. Building on the extensive scholarship about the evolution of property rights, the Article emphasizes the need to take seriously the implications of the political process by which private property often is formed. To underscore its theoretical argument about the evolution of private property, the Article also offers a case study of contemporary property rights formation. For over six decades an international movement has been underway to enclose the oceans, including marine fisheries. Drawing on original research, the Article examines why individual transferable quotas and similar instruments have been slow to develop in U.S. coastal fisheries in federal waters since national jurisdiction over fisheries was extended to 200 miles from the shore in 1976. In closing, the Article underscores the richness of Demsetz’s pioneering account of private property and the scholarship that it has spawned. But the Article also suggests that there remains a large gap between how private property actually evolves and many of the prevailing theoretical understandings of the development of property rights. The Article argues in turn that filling this gap requires developing a more robust positive theory of the evolution of private property that takes into account the political process through which private property often is formed, and more systematic empirical research into the development of property rights.