Chapter 1 examines the space of the Port to provide an economic history of trade in the medieval Indian Ocean. The port serves as a useful lens through which to view the relationships and institutions that made possible the regular exchange of goods across the vast distances of the ocean. The chapter is animated by the question of how trade functioned within this world, and specifically how merchants were able to trust one another despite the distances and differences that separated them. It examines the relationship between ports and oceanic networks, the prominent role played by Muslims within them, and the composition of Muslim trading groups. It argues that the business practices, institutional preferences, and legal framework used by Indian Ocean merchants, Muslims and non-Muslims alike, were all directed towards overcoming the fundamental problem of trust. By examining first ports as the sites of trade, then institutions as the underpinnings of trade, and finally prominent merchants as exemplars of their communities, the chapter reveals the economic foundations upon which the world of Monsoon Islam was built.