1. Stronger industrial base. The North had a much more developed economy than the South, which was largely agricultural. Northern factories produced the vast majority of the war's weapons and ammunition, while Southern factories were often destroyed by Union forces.
2. More men and resources. The North had a much larger population than the South, and could thus field a much larger army. It also had more access to financial resources, which allowed it to purchase weapons and supplies from Europe.
3. Better military leadership. The North's generals were generally more experienced and better-trained than the South's. Ulysses S. Grant, William Tecumseh Sherman, and George McClellan all proved themselves to be capable leaders, while Robert E. Lee and Stonewall Jackson, the South's two best generals, were often hampered by a lack of resources.
4. Superior strategy and tactics. The North's strategy was to defeat the South by destroying its economy and infrastructure, rather than by trying to win a series of decisive battles. This proved to be a sound strategy, as the Union gradually strangled the South into submission.
5. Diplomatic support. The North was able to secure the support of several European countries, including Britain and France, which helped to prevent the South from receiving much-needed aid from abroad.
6. African-American soldiers. The Union Army eventually allowed African-Americans to serve as soldiers, and these troops proved to be a valuable asset. They fought bravely and helped to turn the tide of the war in the North's favor.
7. The Emancipation Proclamation. The Emancipation Proclamation, issued by President Abraham Lincoln in 1863, freed all slaves in the Confederate states. This helped to undermine the South's economy and turn public opinion against the Confederacy.
In the end, the combination of these factors led to the North's victory in the Civil War.