The war that freed the slaves in the United States was the American Civil War (1861–1865). During this conflict, President Abraham Lincoln issued the Emancipation Proclamation on January 1, 1863, which declared that all enslaved people in the rebellious Confederate states "are, and henceforward shall be free"

. The Emancipation Proclamation changed the legal status of more than 3.5 million enslaved African Americans in the secessionist states from enslaved to free, although it applied only to states in rebellion and not to loyal border states or Confederate areas already under Union control

. The proclamation also allowed freed slaves to join the Union Army and Navy, with nearly 200,000 Black soldiers and sailors fighting for the Union by the war’s end

. The Civil War initially aimed to preserve the Union, but from 1863 onward, it also became a war to end slavery

. The Union’s military victory ultimately led to the abolition of slavery, which was formally ended nationwide with the ratification of the Thirteenth Amendment in 1865

. In summary, the American Civil War, through the Emancipation Proclamation and Union victory, freed the slaves in the United States