On June 19, 1865, slaves in Galveston, Texas, were finally informed of their freedom by the Emancipation Proclamation (issued two years prior). The day the last American slaves were freed has become a holiday celebrated officially in 45 states. In the summer of 1862, the Confederates scored one victory after another. President Lincoln believed freeing slaves would weaken the South by greatly reducing its labor force. He prepared a proclamation that would free slaves in the Rebel states, but needed a Union victory to win support in the North. That chance came in September, when Northern forces stopped a Confederate invasion at Antietam, Maryland.