Answer:
because many maintain that the primary cause of the war was the Southern states' desire to preserve the institution of slavery. Others minimize slavery and point to other factors, such as taxation or the principle of States' Rights
The Civil War confirmed the single political entity of the United States, led to freedom for more than four million enslaved Americans, established a more powerful and centralized federal government, and laid the foundation for America's emergence as a world power in the 20th century.