This is a list of cases reported in volume 304 of United States Reports, decided by the Supreme Court of the United States in 1938. Justices of the Supreme Court at the time of volume 304 U.S. The Supreme Court is established by Article III, Section 1 of the Constitution of the United States, which says: "The judicial Power of the United States, shall be vested in one supreme Court . . .". The size of the Court is not specified; the Constitution leaves it to Congress to set the number of justices. Under the Judiciary Act of 1789 Congress originally fixed the number of justices at six (one chief justice and five associate justices). Since 1789 Congress has varied the size of the Court from six to seven, nine, ten, and back to nine justices (always including one chief justice). When the cases in volume 304 were decided the Court comprised the following nine members: Notable Cases in 304 U.S. Erie Railroad Company v. Tompkins Erie Railroad Company v. Tompkins, 304 U.S. 64 (1938), is a landmark U.S. Supreme Court decision in which the Court held that there is no general American federal common law and that U.S. federal courts must apply state law, not federal law, to lawsuits between parties from different states that do not involve federal questions. In reaching this holding, the Court overturned almost a century of federal civil procedure case law, and established the foundation of what remains the modern law of diversity jurisdiction as it applies to United States federal courts. Although the decision is not widely known by laypeople, most American lawyers and legal scholars regard Erie as one of the most important decisions in U.S. Supreme Court history. The decision "goes to the heart" of the American system of federalism and the relationship between the U.S. federal government and the states. Hinderlider, State Engineer v. La Plata River and Cherry Creek Ditch Company In Hinderlider, State Engineer v. La Plata River and Cherry Creek Ditch Company, 304 U.S. 92 (1938), the Supreme Court ruled that a "general common law" or "general federal common law" no longer exists in the American legal system. Federal courts, however, retain the power to create federal common law in specific areas related to federal rights and interests (e.g., the interpretation of an interstate compact governing water rights between states. United States v. Carolene Products Company In