An 1898 literature guide provided this synopsis of the plot:
Tom Grogan, by F. Hopkinson Smith (1895.) is a spirited and most entertaining and ingenious study of laboring life in Staten Island, New York.
Tom Grogan was a stevedore, who died from the effects of an injury. With a family to support, his widow conceals the fact of her husband's death, saying that he is sick in a hospital, that she may assume both his name and business.
She is thenceforth known to all as 'Tom Grogan'. A sturdy, cheery, capable Irishwomen, she carries on the business with an increasing success, which arouses the jealous opposition of some rival stevedores and walking delegates of the labor union, which she has refused to join.
The story tells how, with marvelous pluck, Tom meets all the contemptible means which her enemies employ in order to down her, they resorting even to the law, blackmail, arson, and attempted murder. In all her mannish employments her mother-heart beats warm and true, and her little crippled Patsy, a companion to Dickens's Tiny Tim, and Jenny the daughter with her own tender love affair, are objects of Tom's constant solicitude.
The author has given a refreshing view of a soul of heroic mold beneath an uncouth exterior, and a pure life where men are wont to expect degradation.

Question: What organization does "Tom" resist joining?
Answer: The labor union.
Alternative answer: The labor union