Answer:
Blackface is historic form of performance that was very popular in the United States in the nineteenth and early twentieth century.
Blackface was performed by white actors, who painted their face black, and portrayed African American characters in a stereotypical and offensive manner.
Blackface fell out of favour in the U.S. in the middle of the twentieth century, due to changes in the views of Americans about race, and also due to the influence of the Civil Rights Movement.