The answer is D.
The battle of Gettysburg took place in nothern territory. General Robert Lee led the confederate army into Pennsylvania and brought the war directly into northern territory.
The Union army of the Potomac led by General Meade, met the confederate invasion near the Pennsylvania town of Gettysburg and what began as a chance encounter quickly turned into a desperate ferocious battle and on July 3rd, the battle turned against Lee and he opted to retreat.