Which war ended slavery in the United States?

The Civil War, which took place from 1861 to 1865, was the conflict that ultimately led to the end of slavery in the United States. This war was primarily fought over the issues of slavery and states' rights, with the Union (the North) opposing the Confederate States (the South), which sought to maintain the institution of slavery.

The culmination of the Civil War came with the passage of the 13th Amendment to the Constitution in 1865, which formally abolished slavery across the entire nation. Although there were earlier abolitionist movements and legal freedoms granted in certain states, it was the outcome of the Civil War that resulted in the nationwide legal prohibition of slavery, thus marking a significant turning point in American history.

In contrast, the other wars mentioned—World War I, the Revolutionary War, and the Spanish-American War—did not focus on the institution of slavery and had different objectives and outcomes that did not directly address or result in the abolition of slavery within the United States.