The venerable but underdeveloped assumption that modern urbanization is comprehensible in terms of social struggles for control of great cities' dominant institutions and its corollary that these struggles, in turn, helped shape further urbanization may still bear fruitful suggestions. Abundant evidence, moreover, makes exploration of this proposition eminently feasible in respect to London, Paris, and New York while as the foremost of the world's megalopolises they were acquiring their modern technical and social characteristics between the 1850s and, let us say, 1910. Notwithstanding the uniqueness of many developments in each of them, the complex social conflicts and the roughly similar climates of opinion often marking their evolutions, encourage certain comparisons among them. Such comparisons, hopefully, may illuminate some of the lingering consequences of the megalopolitan middle classes having to protect their new power not only against the potentialities of the working classes but also against the forces of provincialism operative inside as well as outside of their urban bailiwicks.