Which act was frequently misused against labor unions following its passing?

The Sherman Anti-Trust Act of 1890 is the correct answer because it was originally intended to combat monopolistic practices and promote competition by prohibiting anti-competitive agreements and actions. However, after its passage, it was often misapplied against labor unions rather than corporations. Courts interpreted the act in such a way that they viewed strikes and collective bargaining as conspiratorial actions that restricted trade, leading to injunctions against union activities. This misuse significantly undermined the labor movement during the late 19th and early 20th centuries as unions fought for better working conditions and wages.

The Clayton Anti-Trust Act, while also related to antitrust actions, sought to clarify and protect labor unions, specifically exempting them from being classified as illegal combinations in restraint of trade. The Hepburn Act strengthened regulatory powers over the railroad industry, so it does not pertain to labor unions in the same context. The Dawes Act aimed to assimilate Native Americans into American society and has no direct connection to labor unions or antitrust legislation. Hence, the Sherman Anti-Trust Act stands out for its frequent misapplication against organized labor.