The case of St. Louis in the 1940s demonstrates the central importance of this decade in American urban history. To understand how planners and elected officials made such extensive use of federal funds in the 1950s and 1960s for public housing and urban renewal, we have to recast the 1940s as a critical period in the formation both of a new urban vision and of a political coalition emboldened to carry it out. Frustrated in their attempts to rebuild in brick and mortar, slum clearance advocates in St. Louis set about redefining the terms of debate over the future of the city itself. They mobilized behind a vision of the city at a crossroads, poised between progress and decay. Yet despite such stark rhetoric, slum clearance was not so much a technological or economic imperative, but a carefully assembled political agenda to remake the urban landscape.