On January 1, 1863, the Emancipation Proclamation issued by U.S. President Abraham Lincoln went into effect, however it did not abolish slavery. The Proclamation, written the previous September, declared free all enslaved people in the Confederate States (or portions of those states) who resided in territory still in rebellion against the United States. As the Union Army captured more Confederate territory it would also liberate enslaved people living in that territory.
It was only through the Thirteenth Amendment that emancipation/abolishment of slavery in the United States become national policy. It was passed by the US Senate on April 8, 1864, and by the House on January 31, 1865.