On July 3rd 1863!
becaus many many many men died and it was for just a big hill/plain
The Union - a most historic win. Some people called it 'Confederate high watermark'. Together with Grant's occupation of Vicksburg, the same week, and the consequent liberation of the Mississippi, it was a big milestone towards eventual Union victory.
The defense of Little Round Top on Day Two of Gettysburg saved the Union line and set the stage for the final victory on Day Three.
George A. Custer
Shiloh, Antietam, Gettysburg, Lookout Mountain, Atlanta, The Wilderness…
The North - a big factor in Union victory
Although Gettysburg was not entirely a victory for the Union, it was very much a defeat for the South. The Confederate Army was never again able to gain the strength for a significant attack on the Union Armies. The defeat meant that England and France would not recognize the Confederacy as its own country. Furthermore, at the exact same time as the battle at Gettysburg, General Grant was able to crush the opposition and take Vicksburg, the last Confederate stronghold on the Mississippi River. This meant that Union boats and supplies could use the great river. The first week of July, 1863, was very bad for the Confederacy.
A big event was Pickett's charge because although effective the Confederacy still surrendered in the end.
North. It was a big factor in the Union victory. They were able to move whole armies by rail.
By chance, they happened on the same day (4th of July), so they had a big effect on Northern morale. Gettysburg was the more dramatic battle, but Vicksburg was the more significant victory - ending the war in the West, and freeing Grant to go to the aid of the Army of the Cumberland in Chattanooga. It gave him the credibility that would propel him to the top job - General-in-Chief of all the Union armies.
No, Jackson was killed in the big battle of Chancellorsville, about two months before Gettysburg. Gettysburg was the next big battle after Jackson's death, and he was sorely missed by the Confederates.
The last big battle was the Siege of Petersburg, where Grant simply waited for the Confederates to run out of manpower. It was followed by a few days of small engagements ending at Appomattox, where the surrender took place. If you mean 'which battle swung the war?', most people debate between Gettysburg and Vicksburg. (I would cite the latter.)