The Battle of Gettysburg, fought between June 1 and 3, 1863 between Union forces and Confederate forces, was one of the major turning points of the Civil War, as the Union victory stopped the Confederate advance in the territory of the north and left free way for the Union to be able to advance towards the territory of the south.
The battle itself was a massacre, with more than 50,000 dead in total. But in addition to being a military disaster for the Confederacy, it also had implications from a strategic point of view. An eventual southern victory would have implied a clear advance towards New York, which would imply an almost certain victory for the Confederacion. Furthermore, a Confederate victory would have encouraged France and Great Britain to ally with it to defeat the Union, which in those years was a major commercial adversary. Therefore, the victory of the Union in this battle prevented the participation of France and Great Britain in the conflict.
The main reason why the western frontier was an important area for the patriots to control is because this is where many important resources, such as the Mississippi River were located--making it advantageous both for military and transport reasons.
