The Union won the war because:
1) There factories were built up; the South was mostly farms
2) They had the support of African slaves located in the South
3) They had larger armies
4) They had a more built up navy
5) They were able to deprive the South of their economy and allies
hope this helps
To honor the ones who lost their lives during the battle (hope this helped!)
To Contain Communism and Maintain a strong image.