That's so Ghetto

The Columbia Encyclopedia reads, "Ghettos originally were sections of a city where the Jews were compelled by the Christians to reside, but now more loosely used to indicate any quarter of a town inhabited chiefly by Jews.  The first historically authentic ghetto was established in Rome by Pope Paul IV, in 1555.  The medieval ghettos, which usually consisted of a few narrow, dirty, and overcrowded streets with space limitations.  Within the ghettos the Jews developed a certain degree of autonomy, a social life of their own, and high standards of piety and morality.  In 1870, the last remaining ghetto, the Roman one, was abolished by Victor Emmanuel." When did ghettos become synonymous with so called black people?