Which amendment abolished slavery in the United States?

The 13th Amendment to the United States Constitution is the correct answer because it explicitly abolished slavery and involuntary servitude, except as punishment for a crime. Ratified in December 1865, this amendment marked a pivotal change in American law and society following the Civil War. The language of the amendment directly states, "Neither slavery nor involuntary servitude, except as a punishment for crime, shall exist within the United States, or any place subject to their jurisdiction." This constitutional change aimed to ensure freedom and equality for all individuals, affirming the principle that no person could be legally held in bondage.

The other amendments listed do not pertain to the abolition of slavery. The 14th Amendment deals with citizenship rights and equal protection under the law, the 15th Amendment addresses voting rights irrespective of race, and the 16th Amendment establishes the federal income tax. Each of these amendments plays an essential role in enhancing civil rights and liberties, but none of them abolish slavery.