The Battle of Gettysburg was a significant turning point of the Civil War because it prevented a confederate invasion of the North and eliminated about one-third of General Lee's men. The Battle of Gettysburg was a three day battle that took place in Gettysburg, Pa., between July 1st and July 3rd of 1863.
After achieving a major victory over northern forces in Chancellorsville, Va, General Lee decided to push his troops north. His strategy was two fold. First, if he could establish a stronghold in a northern state, he thought he could push his army further into other northern states. Second, since most of the northern troops were actually in the south at the time, he felt that if he could get ahead of the northern troops with a victory in the north and keep them at bay while he dispersed his troops throughout the north. Some northern troops heard of Lee's plan, however, and were able to establish themselves in Gettysburg before Lee and his men got there.
On the third day of the Battle of Gettysburg, the Confederate army suffered a major blow during Pickett's Charge, the primary push of the Southern army against the Union army. Half of the 12,000 Confederate soldiers who were part of the charge died. By the end of the Battle of Gettysburg, more than 28,000 confederate soldiers were dead, and Lee was forced to retreat back into Virginia.