In a comparative analysis of late nineteenth and early twentieth century Rio de Janeiro and New York City, this dissertation reveals how gendered space operated as a powerful structuring tool for the cities and for the bodies of inhabitants. As the physical geography of Rio and New York underwent significant growth and development from industrialization, immigration, and surging nationalism, it destabilized existing spatial divisions, and thus an important mechanism of social control. Consequently, urban development efforts sought ways to modernize the cities' appearance while maintaining hierarchies of sex, race, and class. By focusing on New York City and Rio de Janeiro- this dissertation argues that the gendering of space appealed to ideas of a biological, natural system in a time of rapid change and flux. Yet, the individual ways in which each city structured and enforced gendered space reveals the particular social values and moral codes inherent in these purportedly natural systems. This work also considers the spatial dimensions of body ideals for men and women, and it contextualizes the political, social, and symbolic implications of the movement and display of these bodies within city space, elucidating transnational commonalities and local differences.