Unionist slave-states had abolished slavery by June 1865, and the only place in the USA where slavery was still being practiced was Texas.
Delaware voted on February 18, 1865 to reject the 13th Amendment to the United States Constitution and so voted unsuccessfully to continue slavery beyond the Civil War. Delaware symbolically ratified the amendment on February 12, 1901—40 years after Lincoln's Emancipation Proclamation. Slavery ended in Delaware only when the Thirteenth Amendment took effect in December of 1865.