In this essay, John Dinan describes the role of natural law in the drafting of founding-era state constitutions. Fifteen state constitutions were written before the U.S. Constitution, and as many as half of the delegates to the Constitutional Convention of 1787 participated in the drafting of these state constitutions. Because of this, state constitutions heavily influenced the content of the U.S. Constitution, whose drafters presumed the continued vitality of their pre-existing state constitutions. Founding-era state constitutions characteristically employed the natural law language of the Declaration of Independence and drew on the long tradition of natural law and natural rights political thought to argue for the right to republican government and such inalienable rights as life, liberty, property, happiness, and safety. It is also in the state constitutions that we find claims to the right to emigrate and the right to religious freedom. Although the drafters of the state and federal constitutions were also influenced by the English common law tradition and documents such as the Magna Carta and the English Bill of Rights, there is no mistaking the strong presence of natural law principles in the founding-era state constitutions.