What was the name of the U.S. war fought between the North and the South?

The U.S. war fought between the North and the South is known as the Civil War. This conflict took place from 1861 to 1865 and was primarily centered around the issues of slavery and states' rights, leading to tensions between the Southern states, which seceded from the Union, and the Northern states, known as the Union.

The Civil War was significant in shaping the nation’s history, leading to the abolition of slavery and setting the stage for the civil rights movements that would follow. It was one of the most profound and transformative periods in U.S. history, with a lasting impact on the social, political, and economic landscape of the country.

Other wars mentioned, such as the Revolutionary War, the War of 1812, and the Mexican-American War, were entirely different conflicts with varying causes and consequences, not specifically concerning the divisions between Northern and Southern states in the United States. This context helps clarify why the Civil War is the correct answer to this question.