On September 22, 1862, Lincoln issued a preliminary 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 did so, and Lincoln’s order was signed and took effect on January 1, 1863.
It changed the legal status under federal law of more than 3.5 million enslaved African Americans in the Confederate states from slave to free. As soon as a slave escaped the control of the Confederate government, either by running away across Union lines or through the advance of federal troops, the slave was free. Ultimately, the Union victory brought the proclamation into effect in all of the former Confederacy. The remaining slaves, those in the areas not in revolt, were freed by state action, or by the Thirteenth Amendment to the United States Constitution, ratified in December 1865.