In the American system of dual sovereignty, states have primary authority over matters of state law. In nonpreemptive areas in which state and federal regimes are parallel—such as matters of court procedure, certain statutory law, and even some constitutional law—states have full authority to legislate and interpret state law in ways that diverge from analogous federal law. But, in large measure, they do not. It is as if federal law exerts a gravitational force that draws states to mimic federal law even when federal law does not require state conformity. This Article explores the widespread phenomenon of federal law’s gravitational pull. The Article begins by identifying the existence of a gravitational force throughout a range of procedural and substantive law felt by a host of state actors, including state rulemakers, legislators, judges, and even the people themselves. It then excavates some explanatory vectors to help understand and appreciate why federal law exerts a gravitational force. Finally, the Article considers some normative concerns with state acquiescence to the federal gravitational pull.