Each state’s constitution and laws establish the state’s courts, which interpret state laws (and generally not federal laws). A court of last resort, often known as a supreme court, is usually the highest court in the state. Some states also have an intermediate court of appeals. Below these intermediate courts of appeal are the state trial courts, where most lawsuits begin. State trial courts are referred to differently in different states—often as district courts, circuit courts, or superior courts.

State courts are often courts of general jurisdiction—meaning they hear all types of cases—involving criminal law, family law, probate law, and general disputes involving money and property. But more populated counties often have courts of specific jurisdiction, such as family courts that only hear family law matters (divorce, child custody, child support); criminal courts that only hear criminal matters; and probate courts that only handle the probate of estates and related litigation.

In Oregon, the judicial system is structured with the Oregon Supreme Court at its apex, serving as the court of last resort. Below the Supreme Court is the Oregon Court of Appeals, which is an intermediate appellate court that reviews decisions from the lower courts. At the foundation of the state's judicial system are the Oregon Circuit Courts, which are the general jurisdiction trial courts for the state. These courts handle a wide variety of cases, including criminal, civil, family, and juvenile matters. Oregon does not have separate courts for family, criminal, or probate matters at the trial level; instead, these cases are all heard in the circuit courts. In more populous areas, specialized departments within the circuit courts may be dedicated to handling specific types of cases, such as family or probate law, to ensure that cases are managed by judges with the appropriate expertise. It's important to note that while state courts primarily interpret and apply state law, they may also rule on federal laws to the extent that they apply to cases before them, unless federal law specifies exclusive federal jurisdiction.