This work studies urban form and function in Hispanic American colonial port cities. By combining different research questions and points of view, new insights are given into matters such as the origin of their urban grids, the development of their fortifications throughout the colonial era, and the military versus trade function they accomplished. The focus is on Cartagena de Indias, Colombia, with other Hispanic colonial cities also included in the discussion. The field work is based on primary literature about colonial laws and ordinances and the reports of several viceroys in the eighteenth century as well as a wide array of secondary literature in different languages. The results show that, while these cities fulfilled an important role as trade nodes, this function was second to their military role. However, both functions are found to be interdependent in a number of ways. [ABSTRACT FROM AUTHOR]