This chapter surveys the legal history of the term "due process of law," from Magna Carta, the Statutes of Edward III, and the Petition of Right to the writings of William Blackstone and the opinions of antebellum state-level court cases. It argues that there was no concept of "substantive due process" in the antebellum period. It refutes arguments that due process prohibited class legislation, limited states to reasonable exercises of the police powers, or underwent a change in meaning as a result of abolitionist constitutional thinkers.