Slave state
A slave state is a U.S. state that had legal slavery (overwhelming the enslavement of African-Americans, although historically also the enslavement of Native Americans, and whites through indentured servitude) in the period before the American Civil War and the Emancipation Proclamation. The 15 slave states were Alabama, Arkansas, Delaware, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, Missouri, North Carolina, South Carolina, Tennessee, Texas and Virginia.All but four of these states seceded in 1860 and 1861 to form the Confederate States of America: Delaware, Kentucky, Maryland and Missouri did not leave the Union.
Through most of the early part of the 19th century the U.S. was concerned with maintaining the balance of slave states and free states, as the slave states would not permit themselves to be outnumbered in the Congress and thus risk losing the peculiar institution which was the foundation of their economies. As a result of this preoccupation, slave states and free states were often admitted into the Union in pairs, so as to maintain the existing balance between slave and free.
| Slave State | Free State |
| Missouri (1821) | Maine (1820) |
| Arkansas (1836) | Michigan (1837) |
| Florida (1845) | Iowa (1846) |
| Texas (1845) | Wisconsin (1848) |