The Emancipation Proclamation

After the battle of Antietam, even though it was technically a draw, Lincoln was very confident after the "victory." In fact, he was so confident that he decided to issue the Emancipation Proclamation. The Emancipation Proclamation was an official document that issued the freedom of all slaves in the Confederate States. Because Lincoln technically had no power over the southern states, slaves would have to escape into the North to be free. Lincoln did not free slaves in the border states of Maryland, Delaware, Kentucky, and Missouri because he needed those states to stay in the Union, as they would almost double the population of the Confederacy. This was very controversial, because it went against the Constitution and now the Union was fighting for something other than keeping itself together. In the document, Lincoln encouraged slaves to escape and join the Union army. This way, the Union's already huge population was being combined with angry, determined slaves.

Image From: http://theinterrobang.com/2012/12/the-filtered-excellence-december-27-2012/filtered-excellence-emancipation-proclamation/