With the increasing protracted displacements and overall worldwide migration in recent decades, local integration has been considered a durable solution. Accordingly, global agendas have recommended the inclusion of migrant populations, especially within urban frameworks, as cities have always been deemed as migrant hubs. This study examines the influence of migrant spatial integration in city development and municipal policy against the historic backdrop of Busan. From liberation (1945) to post-war industrialization (1960s–1980s), Busan experienced population surges with the inflow of refugees and migrants that historically changed government policies and urban development plans. Based on archival research, secondary data, and GIS mapping, this study explores the influence of migrant populations on the city demographics, physical development, and housing initiatives during different periods. The findings of this study highlight the “local turn” in migrant spatial integration and the production of new urban geographies that portray “humanitarian” and “migrant” urbanism, thereby offering insights into sustainable urban futures for migrant and displaced populations.