In the late 1800s many employers used blacklisting to

A blacklist is a list of people, institutions or objects that must be discriminated against in some way with respect to those that are not on the list. Discrimination can be social, technical or in some other way. In the USA During the McCarthyism, people denounced as communists or anti-Americans became blacklists. The people included in these lists had great difficulties to be hired. Associated with this, we also see that people who had contacts with the unions entered the black lists, and therefore could not enter to work, or it was very difficult for them to find a job.