This spot on Cemetery Ridge was the farthest that rebels got into the Union line during Pickett's Charge on the 3rd and final day of the battle.
It is called the Angle, and was the one spot along Cemetery Ridge where rebel troops penetrated the Union line during the climax oof Pickett's Charge
It was an unfinished project in July of 1863, when on day one of the Gettysburg battle Federal troops captured scores of Confederates caught at the bottom of the steep walls.