Tenth Circuit Act of 1863

Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled, That the supreme court of the United States shall hereafter consist of a chief justice and nine associate justices, any six of whom shall constitute a quorum; and for this purpose there shall be appointed one additional associate justice of said court, with the like powers, and to take the same oaths, perform the same duties, and be entitled to the same salary, as the other associate justices.The period of the American Civil War and the immediate aftermath of Reconstruction saw shakeups in the Court and in legislation concerning its size.

This culminated in the Judiciary Act of 1869, the last piece of legislation which altered the size of the Supreme Court.

Pursuant to the Tenth Circuit 1863 Act, Stephen Johnson Field was installed in the newly created Associate Justice seat.

Shortly thereafter, Salmon P. Chase replaced Roger B. Taney as Chief Justice of the United States, and in 1865 Associate Justice John Catron died; Catron's vacancy would never be refilled as a consequence of the Judicial Circuits Act of 1866.

Finally, Catron's death and his seat's subsequent abolition ended the "court of ten".