The OED online includes these early published references to "labor unions":
1866 in Documentary Hist. Amer. Industr. Society (1910) IX. 133 Each member belonging to the National *Labor Union.
I think I have unions on my mind because Senator Obama was a labor-organizer, and Senator Clinton's having sat on the Wal-Mart Board (apparently she was a thorn in the Board's side) has become an issue. Meanwhile, the Republicans seem content to leave "the union vote" (whatever that may mean) to the Democrats, and in my profession, college-teachers who aren't in tenure-line positions have been joining unions.
Also, we've been watching a BBC adaptation of Charles Dickens' Hard Times, in which the factory-owner and fabricator of a rugged childhood, Josiah Bounderby, opposes unions. As usual, Dickens tends to shy away from broader structural or political issues and makes everything exceedingly personal, so that one of the characters is sympathetic to the union, speaks forcefully against Bounderby and on the plight of workers, but doesn't join the union because he promised someone once that he wouldn't (and is therefore shunned by his "brothers"). The man's personal code of honor trumps his sense of solidarity. Bounderby fires him anyway, so the man takes off across the countryside to look for work--and falls into coal-mining pit camouflaged by rotten wood and weeds. He dies, but not right away. Dickens loves to squeeze the melodramatic juice out of his plots. The production is a bit long in the tooth; the late Alan Bates plays Bounderby and does a nice job. Published in the same year as Origin of Species (1859), Hard Times is Dickens' send-up of utilitarian education, phony "self-made" tycoons, and the savagery of industrialized England. Tom Gradgrind is the schoolmaster-turned-politician.
Does England have a screen-actors' guild? I assume so, but I need to look for the union label on the DVD-case.