The Union was confirmed by the most industrialized states in the country. This meant that the production of weapons and tools related to war logistics was controlled by them. Besides having more weapons and supplies, the Union also had more soldiers, as the population was considerably bigger in the north.
Railroads are a sign of development. In terms of war, they helped mobilize troops and resources along the country with relative ease in comparison to their Confederate counterparts. This represented a great advantage for the Union.
Besides having the previously mentioned advantages. The Union also had the naval power on their side and executed the blockade in an attempt to cut the resources from The Confederacy. As a response, the southern states replaced the growth of Cotton with other crops in order to have food supplies.