This essay examines the original meaning of the equality guarantee in American constitutional law. It looks are the seventeenth, eighteenth, and nineteenth century roots of the modern doctrine, and it concludes that the Fourteenth Amendment bans the Hindu Caste system, European feudalism, the Black Codes, the Jim Crow laws, and the common law's denial to women of equal civil rights to those held by men. It then considers the constitutionality of bans on same sex marriage from an Originalist perspective, and it concludes that State laws banning same sex marriage violate the Fourteenth Amendment.