Slave states and free states
DIVISION OF U.S. STATES IN WHICH SLAVERY WAS EITHER LEGAL OR ILLEGAL
Slave states; Free state (United States); Slave State; Free state (USA); Slave state (United States); Slave state; Free and slave states; Slave and free states; Slave-holding state; Free states and slave states; Slave state or a free state; Slave state and free state; Free state and slave state
In the United States before 1865, a slave state was a state in which slavery and the internal or domestic slave trade were legal, while a free state was one in which they were not. Between 1812 and 1850, it was considered by the slave states to be politically imperative that the number of free states not exceed the number of slave states, so new states were admitted in slave–free pairs.