Courts of law are located in the judicial branch of government. Generally, courts come in two varieties: trial and appellate. A typical case receives its first hearing in a trial court. Most all cases begin (and end) in trial courts. Some cases require further review after the trial stage; those cases go to appellate courts. The Supreme Court is an appellate court--it hears almost exclusively cases that have been through a trial court and then appealed. Like other appellate courts, the Supreme Court specializes in the interpretation of law. In contrast, much of the work of trial courts is "fact finding": hearing testimony of witnesses and examining evidence. Appeals courts review the legal issues presented in a case only; fact finding is left to trial courts. Thus, no witnesses appear before the Supreme Court, only attorneys.

In the United States there are 51 separate court systems, one for the national government (called the federal court system) and one for each state. Each of the 51 systems has its own structure, and most, including the federal courts, have changed over the years. The following chart shows the current structure of two court systems, one for the U.S. and one for Illinois. Both systems have two levels of appellate courts, with a supreme court on top. Earlier in American history the federal system and many state systems lacked the middle level appellate courts.

The main task of appellate courts is the interpretation of law. In the United States, there are three sources of written law which the courts interpret:

1. Constitutional law--the Constitution and subsequent amendments.

2. Statutory law--laws created by legislative bodies. These laws must be consistent with the Constitution to be valid.

3. Administrative law--rules promulgated by executive branch officers (including the President) or government agencies. These rules must be consistent with the Constitution and with the statutes that the executive officials are attempting to enforce.

The work of the courts in the United States is made more complicated by the fact that law is created at both the state and national levels. Under our system of federalism, the states have their own constitutions and legal system. (For historical reasons the terminology is a bit confusing. "Federalism" specifies a political system made up of a collection of states; "federal" refers to the institutions of government shared by all the states, i.e. the national government.) Each of the three sources of law is found at both the state and national levels in the U.S. legal system. For the most part, state courts interpret state law and federal courts interpret federal law. Federal (national) law is superior in authority to state law. However, the U. S. Constitution, itself a part of national law, in some respects protects the rights of states.

In the cases we will be reading, the Supreme Court is asked to exercise its power of judicial review. This means that in each case the Court determines if a statute (a law passed by a legislature), is consistent with the United States Constitution. If a statute is found to be inconsistent with the Constitution, it is declared null and void by the Supreme Court. In the first case, Plessy v. Ferguson, the Supreme Court is asked to examine a statute passed by the Louisiana State leglislature. That statute recquired separation of people by race when riding in railway cars (the primary means of transportation of that time). Homer Plessy claimed that the statute violated his constitutional rights.