For most of Western history, the majority of people were illiterate; competent lawyers and judges were often in short supply. As England emerged from the Dark Ages, King Henry II instituted custom of having judges ride around the countryside ("ride circuit") each year to hear appeals (rather than forcing everyone to bring their appeals to London). (SeeAssize of Clarendon). Thus, the term "circuit court" is derived from the practice of having judges ride around the countryside each year on pre-set paths to hear cases.
Today, there are federal court of appeals, circuit courts that sit permanently in 14 appellate circuits (11 regional circuits as well as a DC Circuit, Federal Circuit, and Armed Forces Circuit). The federal court of appeals are intermediate courts, between the district courts (the federal trial courts) and the Supreme Court. Smaller circuits, such as the Second Circuit and Third Circuit, are based at a single federal courthouse, while others, such as the large Ninth Circuit, are spread across many courthouses. Since three-judge federal appellate panels are randomly selected from all sitting circuit judges, Ninth Circuit judges must often "ride the circuit," though this duty has become much easier to carry out since the development of modern air travel.
The U.S. Supreme Court justices still retain vestiges of the days of riding circuit; each justice is designated to hear certain interlocutory appeals from specific circuits and can unilaterally decide them or refer them to the entire Court. The Court's customary summer recess originated as the time during which the justices would leave Washington and ride circuit (since dirt roads were more passable in the summer).
