Although the DID is widely used as a statistical unit to identify cities, it does not comprehensively identify urbanized areas due to its high thresholds for both density and size. In this paper, I propose a new unit, Small Urbanized District (SUD), which utilizes basic unit district population statistics of the Census and attempts to identify small cities. As a result, small cities are discovered, especially in areas far from large cities. Analysis of the identified small cities also revealed that they have higher rates of population decline and aging when compared to larger cities.