Congress can create inferior Courts to the one supreme Court, which is the "judcial power of the United States" under Article III.

The Courts created by Congress, like the one supreme Court, "shall extend to all Cases, in Law and Equity, arising under this Constitution, the Laws of the United States, and Treaties made, or which shall be made, under their autority; -to all Cases affecting Ambassoadors, other public Ministers and Consuls; -to all Cases of admiralty and maritime Jurisdiction; - to Controversies to which the United States shall be a Party; -to Controversies between two or more States; -between a State and Citizens of another State;- between Citizens of different States; between Citizens of the same State claiming Lands under Grants of different States, and between a State, or the Citizens thereof, and foreign States, Citizens or Subjects.