The Indian Ocean is traditionally seen as a frontier to the segmented regional entities that lie along its shores, such as the Middle East, South, and Southeast Asia, each of which individually forms a discrete set of social, cultural, and economic study. Recent historical scholarship has challenged such notions by approaching these regions through their interactions across boundaries. Evaluating the Indian Ocean as an economic unit, I study the formation of three types of capitalist systems. First, I look at the degree to which the Indian Ocean formed an integrated market of port cities across the ocean, in comparison to integration over land with interior cities of the colonial hinterland in closer proximity. Second, I measure the resistance and endurance of such transoceanic linkages by estimating trade cost variation through the Suez Canal. Third, I determine the degree to which such an integrated maritime region contributed to economic growth and industrialisation of major regional port cities. My research is motivated by the importance of reconceptualising the historic and economic units of analysis according to capitalist systems of trade and growth as they are defined by the sea, rather than divided by it.