The Battle of Gettysburg refers to an important battle in July 1863, during the American Civil War. Until then the Southern troops called Confederacy successfully invaded the Northern States. However, when they reached Gettysburg in the state called Pennsilvania, a harsh 3 day battle in July, 1863, ended in a confederate defeat. This turned the tide of the war as the Union troops now invaded the Southern states.
Eventually the Union conquered Richmond, the Confederacy capital city, on April 3, 1865. This led to the Surrender in April 26, 1865 ending the war. The secession was reversed and the slaves in the South were free from human ownership