Prior to this, the magazine had already features two black 'playmates', Jennifer Jackson in March 1965 and Jean Bell in October 1969.
Jean Bell was the first black woman to appear on the cover in January 1970, but she had appeared alongside four other models.
In addition to putting black women on the cover of his magazines, Hefner was also a prominent supporter of civil rights.
In 1959 he helped organise the Playboy Jazz Festival, the gross receipts for which funded the civil rights organisation NAACP.
The first interview in Playboy was with Miles Davis, interviewed by black journalist Alex Hayley, and the magazine subsequently interviewed leading civil rights figures such as Malcolm X, Muhammad Ali, and Martin Luther King Jr.