Final answer:
The significant advantage the North had over the South was the larger population and greater industrial capacity. This allowed the North to have ample manpower, produce more goods, and efficiently transport resources, which was crucial for supporting and sustaining the Union's military efforts during the war.
Step-by-step explanation:
The significant advantage that the North held over the South in waging war was its larger population and industrial capacity. The northern states had a population of around 22 million compared to the southern states with around 9 million. This allowed the Union to have greater manpower reserves. Additionally, the North's substantial industrial capabilities, which included 1.3 million workers in factories and the ability to produce nine times as many industrial goods as the South, gave it an upper hand in equipping and sustaining its armed forces.
Moreover, the support for the Union effort was enhanced by its extensive railroad network, allowing for efficient movement of troops and supplies. While southern leaders provided better military leadership and the South had the advantage of fighting a defensive war, the North's overwhelming population and industrial capacity, backed by its superior infrastructure, proved decisive.