In one or more places in each district is held a circuit court of the United States, presided over by any one of the following federal judges, to wit, the justice of the Supreme Court assigned to the circuit, one of the two or more circuit judges of the circuit, and the district judge of the district in which the circuit court is held. Any two of these judges may together hold the circuit court, but any one of them is competent and is qualified to do so. The number of circuits into which the districts are grouped corresponds to the number of justices of the Supreme Court, and each of such justices is permanently assigned to a particular circuit. Formerly it was the practice for these justices to preside over the circuit courts in their respective circuits, but this practice has fallen into disuse, although the authority remains. The circuit judges, two or more of whom are appointed for each circuit, are also judges of the circuit court of appeals, described in the succeeding section, and their time is principally devoted to the discharge of their duties in connection with those courts, so that, as a rule, the ordinary terms of the circuit court in any particular district are presided over by the district judge for the district in which the circuit court is held.

As stated in the preceding section in describing the criminal jurisdiction of the district courts, the circuit courts have jurisdiction to try prosecutions for any crimes against the laws of the United States, and they have exclusive jurisdiction in prosecutions for crimes punishable capitally. But, except as to capital crimes, they do not usually try criminal cases. Their civil jurisdiction includes cases arising under the constitution, laws, or treaties of the United States, provided the matter in dispute exceeds the sum or value of $2,000, and controversies between citizens of different states, or between citizens of a state and foreign states, citizens, or subjects, with a like limitation as to the amount in controversy. Cases of either of these classes which might originally have been brought in a circuit court, if brought in a state court may be removed by the defendant into a circuit court for trial (see above, § 157). Suits by the United States may be brought in the circuit court instead of in the district court, if the amount in controversy exceeds $2,000. There are cases arising under the laws of the United States which may be brought in the circuit court without regard to the amount in controversy: such as suits under the patent or copyright laws, the revenue laws, and the postal laws, and proceedings under the interstate commerce law, the act to protect trade and commerce against unlawful combinations, trusts, and conspiracies, and under the immigration acts.

It is apparent, therefore, that the jurisdiction of the circuit court is usually exercised in civil cases, arising under the constitution, laws, or treaties of the United States, and in cases involving controversies between citizens of different states, or between citizens and aliens; and that this jurisdiction may be exercised, either by trying cases originally brought in this court, or those removed from state courts; but that, save in cases arising under the patent and copyright laws, the revenue laws, the postal laws, and a few other classes of cases, the amount in controversy must exceed $2,000, to give the circuit court jurisdiction.