On September 22, 1862, Lincoln had issued a preliminary proclamation warning that he would order the emancipation of all slaves in any state that did not end its rebellion against the Union by January 1, 1863. None of the Confederate states restored themselves to the Union, and Lincoln's order, signed and issued January 1, 1863, took effect. The Emancipation Proclamation outraged white Southerners (and their sympathizers) who envisioned a race war, angered some Northern Democrats, energized anti-slavery forces, and undermined forces in Europe that wanted to intervene to help the Confederacy. The Proclamation lifted the spirits of African Americans both free and slave. It led many slaves to escape from their masters and get to Union lines to obtain their freedom.
That President's opponents were viscerally, emotionally, strongly against this Executive Order, also.
Link: Emancipation Proclamation