Why was the battle of Gettysburg known as an important turning point in the Civil War?

The Union victory at Gettysburg is regarded as an important turning point--the "high-water mark of the Confederacy"--because it ended in the repulse of the final Confederate invasion of the North. There was still much hard fighting left, but after Gettysburg, the Confederate Army in the eastern theater of the war fought only strategic defensive actions, defending the capital city of Richmond. Additionally, had the Confederates been able to defeat the Union Army at Gettysburg, the way would have been open for a campaign, or at least a move against, Washington D.C.. While such a campaign is unlikely to have been successful, it could have considerably altered the military and political dynamics of the war. The other reason Gettysburg was such a significant turning point was the casualties suffered by the Army of Northern Virginia. More than one-third of Lee's army was killed, wounded, or captured at this battle, and he would never be able to fully replace these numbers for the rest of the war. Finally, the result of the battle was so important because of timing. One day after the battle, on July 4, 1863, Vicksburg, the Confederate stronghold on the Mississippi, fell to troops under Ulysses S. Grant. So in four days, the Union had repulsed a Confederate invasion of the North and seized control of the Mississippi River.