Federalism, the division of sovereign power between national and state governments, creates perpetual tension over the degree of power possessed by each level of government. Innovating such a division in 1787, the framers of the U.S. Constitution could offer only an impressionistic blueprint. Granting the new national government power with regard to several broadly worded subjects, the framers left the details—and thus the precise division of power—to future development. How much power did those grants actually bestow on the national government of the United States? Chief Justice John Marshall’s 1819 opinion in McCulloch v. Maryland was the foundational Supreme Court decision that initiated the process of answering that question, which very much remains relevant in modern times.