Saying the Battle of Gettysburg was the "Turning Point" of the civil war is a bit ambiguous. The South lost the War the day they fired on Fort Sumter, they never had the manpower, industrial resources or the financial capacity to wage a war.
Those that consider fighting the battles as a key to establishing Southern Independence I would consider the appointment of U.S. Grant as Lieutenant General a true turning point of the Civil War. Grant instituted an all fronts offensive fighting policy that denied the South the typical after battle retreats, regroupings, reorganizations and new commander appointments the North would normally go through. Grants fighting strategy and aggressiveness doomed the South.