14 Stat. 209
July 23, 1866

In the first major legislation dealing with the judiciary after the Civil War, Congress redrew the boundaries of the judicial circuits and reduced the number of circuits from ten to nine. It also provided for the gradual elimination of seats on the Supreme Court until there would be seven justices rather than the ten authorized in 1863. Although Congress would increase the size of the Supreme Court within three years, the geographical outline of the circuits has since remained largely the same except for the addition of new states to existing circuits and the division of two large circuits in the twentieth century.

The subsequent stability in circuit organization ended a period of frequent rearrangement of the states within the circuits. After establishing nine circuits in 1837, Congress in 1842 shifted several southern states in order to accommodate transportation routes used by the justices on circuit. In 1862 Congress incorporated six additional states into a restructured system of nine circuits, and within another year had abolished the California Circuit, placed California and Oregon in a Tenth Circuit, and reorganized the midwestern states to make travel easier.

The geographical reorganization of the circuits in 1866 coincided with the broader effort of the Republican majority in Congress to reduce what it saw as the disproportionate influence of southern states in the federal government before the Civil War. Between 1837 and 1862, five of the nine circuits consisted exclusively of slave states. The tradition of appointing a justice from each circuit allowed Southern slaveholders to dominate the Supreme Court. After taking an initial step to reduce the number of southern circuits in 1862, Congress in 1866 left only two circuits composed entirely of former slave states, and only one was composed solely of former Confederate states.

The reduction in the size of the Supreme Court nullified the pending nomination of Henry Stanberry to the tenth seat on the Court and prevented President Andrew Johnson from appointing a justice during the remainder of his term. The legislation owed less to the Republican opposition to Johnson, who signed the act, than to the efforts of Chief Justice Salmon Chase. The first draft of the bill proposed a return to nine justices, thus preventing tie votes on the Court and providing a justice for each circuit. In private communication with influential members of Congress and fellow justices, Chase urged a further reduction in the number of seats in hopes of winning approval for an increase in the justices' salaries. Congress did not approve an increase in judicial salaries until 1871, after it had returned the Court to nine seats.

Further reading:
Kutler, Stanley I. "Congress and the Supreme Court: The Game of Numbers and Circuits." In Judicial Power and Reconstruction Politics. (Chicago: The University of Chicago Press, 1968), 48-63.