The U.S. president who issued the Emancipation Proclamation was Abraham Lincoln. This landmark executive order was signed on January 1, 1863, during the Civil War. It declared that all enslaved people in Confederate-held territory were to be set free, although it did not immediately free any slaves as it could not be enforced in those areas. However, it transformed the war's purpose, adding a moral imperative to the Union's fight. It also paved the way for the eventual abolition of slavery in the United States, culminating in the 13th Amendment to the Constitution in 1865.