A few reasons:
1. General Lee wanted to win a battle on Northern soil to steer Union forces away from the situation at Vicksburg.
2. Lee's army needed supplies and raw materials that couldn't be obtained easily in the Confederacy, and planned to get them from northern farms and warehouses.
3. There is a story that he heard about the shoe factories in the North, but if that is a reason at all, it probably isn't the most important thing to know.
1. General Lee wanted to win a battle on Northern soil to steer Union forces away from the situation at Vicksburg.
2. Lee's army needed supplies and raw materials that couldn't be obtained easily in the Confederacy, and planned to get them from northern farms and warehouses.
3. There is a story that he heard about the shoe factories in the North, but if that is a reason at all, it probably isn't the most important thing to know.
