This article examines the disparity exhibited across the state of Illinois in the proportion of foster youth who remain in care beyond 18, exploring potential sources of this variability. Findings indicate that individual-level characteristics account for a small proportion of the variability. The state’s child welfare agency is administered at the state level and organized regionally. Dependency courts are organized primarily at the county level. An analysis of state child welfare and juvenile court administrative data shows that a significant level of variation in retention rates is found at the county level, suggesting that court-level practice may be influencing the variability evinced by Illinois. Institutional theory and Lipsky’s street-level bureaucracy framework illuminate how courts may be an important source of variation, and a potential target for policy intervention to extend care to more youth.