workingclasshistory:

On this day, 24 September 1883, in a speech in Louisville, Kentucky, Frederick Douglass criticised trade unions that refused to organise Black workers. He complained that the average Black worker “is rejected by trade unions, of every trade, and refused work”. And he cautioned: “It is a great mistake for any class of laborers to isolate itself and thus weaken the bond of brotherhood between those on whom the burden and hardships of labor fall. The fortunate ones of the earth, who are abundant in land and money and know nothing of the anxious care and pinching poverty of the laboring classes, may be indifferent to the appeal for justice at this point, but the laboring classes can not afford to be indifferent. What labor everywhere wants, what it ought to have and will some day demand and receive, is an honest day’s pay for an honest day’s work. As the laborer becomes more intelligent he will develop what capital already possesses – that is the power to organize and combine for its own protection. Experience demonstrates that there may be a wages of slavery only a little less galling and crushing in its effects than chattel slavery, and that this slavery of wages must go down with the other.”
However, most unions in US would ignore him and maintain whites-only memberships, with some notable exceptions like the Industrial Workers of the World. This weakened them and enabled employers to play off different groups of workers against each other in various disputes. Even after unions were eventually desegregated, nearly a century later many unions even with significant levels of Black membership maintained predominately white leaderships, and ignored the concerns of Black workers. This state of affairs was challenged and eventually largely overturned by self-organised Black workers.
One example of this was the case of the League of Revolutionary Black Workers in Detroit: https://workingclasshistory.com/2018/08/28/e12-the-league-of-revolutionary-black-workers-in-detroit/ https://www.facebook.com/workingclasshistory/photos/a.296224173896073/1537216756463469/?type=3