Blackface is an American theatrical make up that has come to be identified with racism.
In the past white performers used burnt cork to color their faces black. Later greasepaint and shoe polish was used. Also the lips were also darkened to make them appear large what was known as "Ubangi lips"
This style of make up was popular in the United States from about 1830-1920. It went into decline during the 20s and 30s and was eliminated from mainstream theatre by 1940. It continued in smaller live theatres, on college campuses and private clubs, until the mid 1960s. By then the social climate of the United States made blackface outdated and overtly racist.
Due to the racial aspects of minstrel shows, which were the main form of theatre entertainment, blackface dominated theatre in the United States. Minstrel shows highlighted black dialect, and spoofed aspects of slave life. Minstrel shows went into decline after the American Civil War and were no longer the main form of American theatre by 1880.
As vaudeville and burlesque replaced the minstrel show, blackface was carried over for no reason other than acts had "always" been done that way, even though the shows no longer featured the black dialect humour. Blackface was quickly dropped from burlesque and more slowly from vaudeville.
Blackface today is considered an intolerable insult to African Americans.