This chapter documents the historical evolution of the US urban system. From a handful of port cities in the colonial period, there was a sustained urban growth from 1830 to the twentieth century. While the initial rise is associated with a transportation revolution and early industrialization, regional shocks associated with immigration, second industrial revolution, gold and oil discoveries, and land speculation give special character to US urban development. The rank-size analysis of city sizes shows that there were three periods of urban hierarchy, largely coinciding with functional evolutions of cities: first, as regional mercantile centers; second, as national, industrial-mercantile, densely built cities; and, third as post-industrial, service-oriented, metropolitan, suburban places. A more detailed analysis of post-industrial cities shows that innovations in services such as finance, insurance and real estate contribute significantly to the concentration of few large metropolitan areas whereas manufacturing and retail tend toward medium and smaller cities. The larger cities were considerably more economically diverse than smaller cities, and a spatial analysis indicates that cities tend to co-evolve as they compete to grow. The chapter concludes with an analysis of the impact of political institutions on urban development. In contrast to developments in Latin America and Canada, American federalism that grants significant political authority to state and localities has significantly impacted US urban and rural development.