First, let's take into account that the battle of Gettysburg started by accident. The roads were the thing that lead to the battle. As more soldiers walked the roads, it turned into the largest battle in the Western hemisphere. The significance of this is that if the battle had not happened there would have
not been all the lives lost.
Now, throughout the battle the union another mistake that was critical to their loss was that General Ewell did not attack the high ground. On the high ground the union was digging in the ground, making defenses or breast works. If General Ewell had taken the high ground the union would have had to retreat. This would have meant that the South would have had its first victory in the North but they also could keep advancing on the retreating union.
The thing that killed tons of people… Amputation was the only way to treat the severely wounded. The Minie ball, a deadly bullet, was one of the causes for all the amputations in the Civil War. The Minie ball was invented by Claude Minie a French Captain. The Minie balls groves had bacteria in them so when it entered the body the bacteria let off the bullet and spread throughout the body.
Finally, lets talk about the rifling in the musket. The rifled musket is a new weapon. The grooves help the bullet spin making it more accurate and deadly. On impact the bullet shatters bones and tears through the muscle and tissue. This why so many people had to get amputation. If the rifled musket had not been invented there may have not been so many horrible wounds.
This is why the battle of Gettysburg was so significant. It was all in part to the technology and the town it self.