Article Three of the United States Constitution
In both Section 1 and in Article One, Section 8, the Constitution gives Congress the right to create courts that are "inferior" to the Supreme Court.  However, the Constitution does not say how many "inferior" courts there should be, or how they should be set up.  It leaves those decisions to Congress.  Congress decided to create two different kinds of "inferior" courts (also called "lower courts").  In the Judiciary Act of 1789, they created: