Who determines the number of federal courts in the United States?

The correct answer is Congress because the U.S. Constitution grants Congress the authority to establish and organize federal courts. This power is derived from Article III, Section 1, which states that "the judicial Power of the United States, shall be vested in one supreme Court, and in such inferior Courts as the Congress may from time to time ordain and establish." This means that while the Supreme Court is the highest court, it is up to Congress to determine the structure and number of lower federal courts, such as district and appellate courts. The President does not have the authority to unilaterally create or eliminate federal courts, and state legislatures are focused on state-level judicial systems, not federal. Thus, the legislative branch, represented by Congress, plays a pivotal role in shaping the federal judiciary.