No one seriously questions the familiar association either between levels of urban development and degrees of industrial maturity or between rates of change in these two indices. It has even become commonplace in macroeconomic growth theory to simplify the complexities of structural change into some variation of the urban-rural two-sector model although, in the real world, shifts from commercial to industrial urban employment, let alone more complex intersectoral shifts, are of prime importance. Indeed, many of these growth models place great emphasis not upon changes in sector productivity but upon resource shifts between low- and high-productivity employment, while in empirical studies urban and rural population data very often appear as explicit substitutes for sectoral employment. But given the paucity of macroeconomic data for the antebellum period, especially prior to 1839, one is left puzzled by our relative inattention to the wealth of population census data by residence. American economic history textbooks are stuffed with quantitative information on the number of cities, their spectacular growth, and the percentage of population urbanized, but these may not be the most effective uses of this great data pool. The plethora of urban histories and the abundant attention to urban rivalry may be useful complements, but they are not very effective substitutes for quantitative analysis of overall American urbanization and experience with city size distribution. The very attention which the topic is currently receiving by economists, geographers, and historians suggests that much remains undone in the study of early American urbanization.