Macao and Hong Kong were founded as port cities for the China trade around 1557 and 1842, respectively. This paper discusses the rich but understudied urban history of these two cities. The paper adopts an evolutionary perspective and uses three research vectors: (i) the nature of the relations between the cities and their respective hinterlands, (ii) the role and character of mercantile elites, and (iii) their urban morphology. The argument is that what enabled these two cities to survive as colonial cities on the South China Sea was their ability to adapt to or transform their environments, and to establish social, cultural, economic and political dynamics with China and with other neighbouring countries. One of the key findings is that the urban history of these cities is crucial to understanding their current roles in the local, regional and global urban hierarchy.