This study rehabilitates concepts from classical human ecology and synthesizes them with contemporary urban and environmental sociology to advance a theory of urbanization as socioenvironmental succession. The theory illuminates how social and biophysical phenomena interact endogenously at the local level to situate urban land use patterns recursively and reciprocally in place. To demonstrate this theory we conduct a historical-comparative analysis of hazardous industrial site accumulation in four U.S. cities, using a relational database that was assembled for more than 11,000 facilities that operated during the past half centuryﾗmost of which remain unacknowledged in government reports. Results show how three iterative processesﾗhazardous industrial churning, residential churning, and risk containmentﾗintersect to produce successive socioenvironmental changes that are highly relevant to but often missed by research on urban growth machines, environmental inequality, and systemic risk.