The leader of the Union was President Abraham Lincoln. He was anti-slavery and was part of the Republican party. He also was the man that put forth the Emancipation Proclimation.
Ulysses S. Grant was the leader of the Union military. Grant was seen as the best general the Union had. He led the Union army to victory.
The Unions plan of attack was named the Anaconda plan. It entailed blockading the Confederacy's sea trade routes. Dividing their forces and cutting communication. Then finally crush their armies.
The Union had a much stronger industrial force than the south. This allowed them to produce more supplies and weaponry.
The Union or North had a much larger population than the south, which caused them to have a larger army and a larger workforce supporting the war effort.
The Union or North had almost all of the railroad industry. After striking a deal with the company owners to put the railways under Government control the army was now able to move troops and supplies to the front lines much faster. They also could transport wounded faster which resulted in saved lives.