The Emancipation Proclamation was actually issued twice. President Lincoln issued it the first time in September of 1862 to try to get the southern states to stop their rebellion. The southern states did not stop their rebellion so January 1, 1863, President Lincoln issued the final Emancipation Proclamation.
The Emancipation Proclamation was a firm demonstration of the President's executive war powers. At first, Lincoln's advisors did not support the Emancipation Proclamation. It was only after a continued commitment from Lincoln and a victory at Antietam that he gained the support of his cabinet members.
The Emancipation Proclamation changed the focus of the war from not only preserving the Union but to also freeing slaves.
The Emancipation Proclamation led the way to total abolition of slavery in the United States. When the proclamation was first issued, it only freed slaves in the rebellious states. By the end of the war, the Proclamation had prepared all citizens for the complete abolition of slavery in both the North and the South. The 13th amendment, which abolished slavery in the United States, was passed on December 6, 1865.