Slavery in the United States was governed by an extensive body of law developed from the 1660s to the 1860s. Every slave state had its own slave code and body of court decisions. All slave codes made slavery a permanent condition, inherited through the mother, and defined slaves as property, usually in the same terms as those applied to real estate. Slaves, being property, could not own property or be a party to a contract. Since marriage is a form of a contract, no slave marriage had any legal standing. All codes also had sections regulating free blacks, who were still subject to controls on their movements and employment. After emancipation, freed slaves were often required to leave the state in which they had been enslaved. The printed slavery code exhibited here was published in March 1862, just one month before slavery in the District ended.