Anarchists among immigrants provide a strong intellectual, cultural, and organizational infusion to American anarchism and American labor organizing more broadly. Anarchists made a point of organizing among and with every kind of person on all kinds of issues. Anarchist newspapers in German, Czech, Yiddish, and more circulated broadly. In fact, the depiction of anarchist as bearded bomb-throwers likely stems from anti-worker newspapers depicting Johann Most, a German anarchist and polemicist who was so influential in US politics that his visage became the icon of anarchism for generations of liberal critics.
As worker exploitation became more savage, anarchists were increasingly the people most willing to directly resist exploitation. Throughout the 1870s, workers in general found their efforts for labor relief frustrated at every turn. Strikes were met with incredible violence from private security and the police alike, worker parades and demonstrations faced threats from business owners and court challenges (the first gun control law in the US that went to the Supreme Court was a law restricting the right of working people to form community defense groups with longarms), and voting efforts were defeated by political machines or enacted only toothless laws. Anarchists, with their willingness to engage in direct confrontation, became more appealing than the moderates to many workers: when moderate means are getting you killed the radicals make a lot of sense.
In the early 1880s, union workers pushed their unions to convene meetings to push towards a general strike for an 8 hour work day. May 1st 1886 was picked, giving organizers a couple years to prepare. While many anarchists were initially skeptical it became clear that there was massive support among working people, and anarchists quickly moved to organize for the fight that was wanted. After all, anarchists don't believe in lording over people, so even if the 8 hour day sounded too modest to many anarchists, who were they to tell their fellow workers to pick a different fight?