at the start of the civil war, there were 34 states in the united states, 15 of which were slave states. of these, 11 slave states declared their secession from the united states to form the confederacy. the slave states that stayed in the union were maryland, missouri, delaware, and kentucky, and were referred to as the border states. by the time the emancipation proclamation was made in 1863 tennessee was already in union control. so the proclamation applied only to the 10 remaining confederate states. abolition of slavery also became a condition of the return of local rule in those states that had declared their secession. the thirteenth amendment to the united states constitution abolished slavery throughout the united states on december 18, 1865, ending the distinction between slave and free states.