This study reconsiders the significance of the intellectual perceptions of the "city" in the history of the United States. By reviewing the public discourses of urban elites in early twentieth-century Chicago, I try to elucidate the rise and fall of "city consciousness, " or the historical city identity as an indivisible organic unity. This work leads to the further exploration on another aspect of the same development, that is, the origin of the current civic image as one of ecologically divided space. Is the city a socially integrated entity or a space with many boundaries defined by class, gender, religion, race and so on? I observe a historical dynamism of the twentieth-century urban history in the intersection of these two interrelated ideas of the modern city. More concretely, this article approaches the historical perception of the city, by examining the characteristics of urban environmentalism in the following three intellectual trends: (1) tenement reforms conducted by social settlement houses, (2) the Chicago Plan, a city planning movement, and (3) the Chicago School of urban sociology. The tenement reforms led by the progressive social workers, such as Jane Addams of the Hull House, who were dedicated to improving poor people's housing, represent a new trend of environmentalism. Their positive engagement with the physical conditions of slum areas differed from the separate-sphere ideology of the preceding Victorian elites. This essay contends that the tenement reformers' endeavors to bridge different groups in the city, gave rise to an inclusive "city consciousness" in Chicago. I argue, however, the new positive environmentalism espoused by tenement reformers was fundamentally compatible with the contemporary exclusion of ethno-racial minorities, quite paradoxically. While the reformers came to understand urban environment as a social issue, their interests in public health and social hygiene increased. They thought clean and healthful physical conditions were indispensable to decent citizenship. This idea would unintentionally produce a social mechanism to stigmatize the poverty among new immigrants and African Americans from the South with a metaphor of contagion and alienated them from civic life. The Chicago Plan, a city planning movement sponsored by local business circles was another source of "city consciousness" in the early twentieth century. Its positive commitment to the urban landscape and park system helped Chicagoans to imagine the city as a comprehensive whole. In this field, innovative public relations activities led by Walter Moody, a sales specialist employed by the Plan Commission, contributed much to creating a sense of city loyalty. This rise of a new generation of professional personnel in the causes for large-scale renovations of built environments is worthy of further examination. Civic identity reached its apex in the 1910s, however it suddenly collapsed during World War I. Encroached upon by wartime federal mobilization, both urban reform and city planning had to justify their causes in terms of appeals to nationalism. I consider this as the beginning of the decline of the idea that city was an indivisible organism. In actuality, Chicago's war experiences were followed by the eruptions of ethno/racial antagonism. The race riots in the summer of 1919 were the worst in its history. It is in this context that the rise of the Chicago School's new urban sociology should be understood. A prominent feature of the scholarship of Robert E. Park and Ernest Burgess was their mapping of the segmented urban spaces sometimes occupied by ethno-racial primary groups. Their perception of the city was quite different from those of tenement reformers and city planners in that Park's human ecology and Burgess's concentric development thesis fundamentally affirmed the pluralist model of urban environments. Furthermore, it is significant that Park took the initiative on the Chicago Commission on Race Relations,