State constitutions serve not merely as institutional design for and restrictions on state government; they also declare and teach fundamental principles. One such principle, America’s existence as a federalist system, appears in almost one in four state constitutions today in the form of what one could describe as proto Tenth Amendment, declaring it to be the right of the state to regulate its internal affairs either exclusively or unless delegated. After consulting every state constitution in history, this research note assembles a comprehensive database of the language and presence of these provisions, including histories of the two states’ decisions to weaken such language. This note will briefly argue that such provisions are not simply a vestigial artifact of a pre-constitutional age, or, alternatively, of an anti-constitutional protest against Reconstruction, but occur throughout the duration of American political development and appear in the North and South, progressive and conservative states.