State and local mental health agencies have responsibility for the psychiatric care of Medicaid beneficiaries and indigents meeting pre-defined criteria. A significant uninsured caseload may prove draining to agencies and hospitals mandated to provide emergency services, resulting in limited access. A spatial needs assessment was conducted to find areas having a greater relative proportion of indigent psychiatric hospitalizations. Robust descriptive and inferential spatial techniques were applied to California 1999-2003 public-use Zip-Code-level hospital discharge data to create maps. These maps reveal a more stable view of spatial variation in the proportion of indigent discharges compared to all psychiatric discharges. Synthetic estimation techniques were also applied to U.S. Census data to estimate the proportion of severe mental illness among households at less than 200% poverty level compared to estimated mental illness among all households. Visually comparing these maps suggests areas of potential mismatch. These results and methods may inform public decision-making.