What was the purpose of the 13th amendment?

The purpose of the 13th Amendment was to abolish slavery throughout the United States.

Explanation:

The Thirteenth Amendment to the United States Constitution officially abolished and continues to prohibit slavery in the United States of America, and, with limited exceptions (such as those condemned for a crime) prohibited involuntary servitude.

At the time of its ratification, slavery remained legal only in Delaware, Kentucky, Missouri, Maryland and New Jersey. In the rest of the United States, slaves had been freed by the state action and the "Emancipation Proclamation" of the federal government.