(Adding on to the other gentleman's answer) It was also a major turning point in the war where General Robert E. Lee's Army of Northern Virginia crossed north over the Potomac River (near modern day Maryland) into the Union, they were finally on the offensive. They ultimately chose to move towards the small town of Gettysburg to acquire shoes for their troops, the Union army met them there on the field. The Confederates ended up being defeated and throughout the rest of the war they never seemed to recover from the battle. Hope I helped.
