What major conflict took place between 1861 and 1865 involving the Northern and Southern states?

The major conflict that took place between 1861 and 1865 involving the Northern and Southern states is known as the Civil War. This war was primarily driven by tensions over issues such as states' rights, economic differences, and, critically, slavery. The Northern states (the Union) and the Southern states (the Confederacy) fought over these contentious issues after several Southern states seceded from the Union.

The Civil War is significant in American history as it led to the abolition of slavery and paved the way for Reconstruction, shaping the future of the United States in terms of civil rights and federal versus state authority.

The other conflicts listed are from different time periods and involve different countries or contexts. For example, World War I occurred later, from 1914 to 1918, involving many nations across the globe; the Revolutionary War took place between 1775 and 1783, leading to the independence of the United States from British rule; and the Spanish-American War happened in 1898, focused on the United States’ intervention in Cuba and resulted in the U.S. acquiring territories like Puerto Rico and the Philippines. Each of these wars is significant but does not pertain to the specific time frame or the North-South divide