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The quantitative urban system structure in historical periods and the long time-scale urban land area grid dataset with spatial attributes are important for land use and land cover change (LUCC) research. In this study, we aimed to measure the area of county level and above cities in mainland China in the 1930s, also known as the traditional Chinese era (TCE), using a geographic information system (GIS) model and 1:50,000 military topographic maps. Furthermore, we aimed to identify the structure and characteristics of the urban system in the TCE according to the administrative area division using methods such as the rank size law. The results of this study revealed that 1265 county level and above cities existed in the TCE, including 25 provincial level or above cities, 179 prefectural level cities, and 1061 county level cities. The total land area of all of the cities was 1396.48 km2, with a mean value of 1.1 km2 and a standard deviation of 2.37 km2. The rank-size analysis indicated that the urban system in TCE was characterized by large cities with insignificant development (q = 0.829 < 1, R2 = 0.905). The results of the Lorenz curve and Moran analyses showed that the spatial distribution of the urban systems in China during the traditional period exhibited nonuniform agglomeration. Large-scale military topographic maps of historical periods have proven to be a good source for land use reconstruction. The 1° × 1° grid urban land area dataset constructed based on a GIS model in the TCE is important for future research on historical LUCC and can provide basic data for climate change models, urban economic history, and other disciplines.