How was the Sherman antitrust act of 1890 used against unions?

The Sherman Antitrust Act of 1890 was initially intended to combat monopolies and promote competition, but it was also applied against labor unions. Courts interpreted the Act to classify unions' collective actions, like strikes and boycotts, as illegal combinations that restrained trade. This led to several legal actions against unions, effectively undermining their ability to organize and advocate for workers' rights. The use of the Act in this way highlighted the tension between labor movements and corporate interests during that era.