If any one proposition could command the universal assent of mankind, we might expect it would be this -- that the Government of the Union, though limited in its powers, is supreme within its sphere of action. This would seem to result necessarily from its nature. It is the Government of all; its powers are delegated by all; it represents all, and acts for all. Though any one State may be willing to control its operations, no State is willing to allow others to control them. The nation, on those subjects on which it can act, must necessarily bind its component parts. But this question is not left to mere reason; the people have, in express terms, decided it by saying, "this Constitution, and the laws of the United States, which shall be made in pursuance thereof," "shall be the supreme law of the land," and by requiring that the members of the State legislatures and the officers of the executive and judicial departments of the States shall take the oath of fidelity to it. The Government of the United States, then, though limited in its powers, is supreme, and its laws, when made in pursuance of the Constitution, form the supreme law of the land, "anything in the Constitution or laws of any State to the contrary notwithstanding."
McCulloch v. Maryland, 17 US 316 (1819).