The Constitution creates only one court, the Supreme Court, and leaves everything else to Congress: every district court, every court of appeals, the number of justices, and much of what the courts may hear all rest on statute.
Read the clause itself, verbatim and in plain language, in the in-app Constitution.
Congress
Congress has set the Supreme Court's size anywhere from five to ten seats (nine since 1869), built the three-tier system in stages (circuit courts of appeals arrived in 1891), and controls jurisdictionA court's legal authority to hear a case: over the subject matter, the parties, and the territory.Full definition in the glossary through 'exceptions and regulations'. Court-expansion and jurisdiction-stripping proposals are this power flexing, whatever one thinks of them, they are constitutional levers, not glitches.
Constitution Annotated, Article III
Terms to know: jurisdictionA court's legal authority to hear a case: over the subject matter, the parties, and the territory.Full definition in the glossary
