The North had a number of advantages over the South.
First, the North was a country recognized by other countries of the world. It would have an easier time getting loans from other countries during the war.
Second, the North had a much larger navy than the South. This would help the North blockade the South in the war.
Third, and most importantly, the North simply had more of what you might call “brute strength.” It had many more people. This was particularly true when you consider that many Southerners were slaves who would not be fighting for the Confederacy. The North also had much more industry. This meant that it could produce all of the things it needed to feed, clothe, and equip its soldiers. The South needed to import, which was a problem given the fact that the North was able to blockade the South. The North had more railroads on which to move troops and supplies around.
Thus, the North had some very important advantages going into the war.