Why was Gettysburg a turning point in the civil war?

Answer 1

Meade forced Lee to abandon his invasion, to retreat back to Virginia, never to invade the North again, seizing the initiative for the North for the rest of the war.

Answer 2

It is the turning point of the war in the East because Meade forced Lee to retreat and abandon his invasion of the North, taking the initiative from him. Lee never invaded the North again and the North never relinquished the initiative from then on.

That said, the true turning point of the was was Grant's capture of Vicksburg, closing the Mississippi to Southern traffic, choking off reinforcements and supplies from reaching Rebel forces.

Answer 3

Lee's defeat ruined his chances of successfully invading the North and swung the initiative to the Union.