The role played by State supreme courts is defined in terms of three relationships: with Federal courts (vertical judicial federalism), with courts in other States (horizontal judicial federalism), and with other institutions of State government. However, State supreme courts are also institutions of State government, affected by State law which regulates the types of cases the court can adjudicate, determines the authority of the court to regulate its workload and focus on certain cases, and provides most of the legal requirements the court is to apply and enforce. The supreme courts of Alabama, Ohio, and New Jersey were examined in detail; they were chosen because those States have an intermediate court of appeals and were politically, legally, culturally, and demographically diverse. The most noteworthy findings were that State supreme courts develop distinctive institutional identities responding to the specific situations in their States; that the law enunciated by these courts can change gradually or rapidly; and that national legal and political influences, such as judicial reform and civil rights, combine with intrastate legal and political factors to impact significantly on the State supreme courts.