Robert “Yank” Smith
Born on the Brooklyn waterfront to a longshoreman father, Yank ran away from home to escape beatings and his parents' fighting. He also worked on the waterfront until he shipped off as a stoker, thus beginning the only life he has ever known. He is proud as the strongest among the stokers, but his encounter with Mildred sends him into a spiral of doubt and rage.
Paddy
An Irish stoker on the ocean liner who seems to have lost hope in the world and wishes for the more glorious days of sailing when the love of the sea was what drove a man. He alone is able to exert some sort of influence over the stubborn Yank.
Long
A stoker on the ocean liner who tries to convince Yank, as well as the other stokers, to believe in the Socialist cause, stressing to Yank that it is not a solution found by brute force but by persuasion and the peaceful uprising of the working class. He takes Yank to Fifth Avenue to try to awaken class consciousness in him, but finds that Yank only goes straight for violence.
Mildred Douglas
The daughter of the president of the Steel Trust, she expresses a desire to “know how the other half lives” by witnessing the working class in its element. In this way, she desires to find her place in the world and give herself a purpose somehow by helping the less fortunate, though, despite this, O’Neill describes her as insincere and pretentious. She is ultimately disgusted and terrified by Yank’s composure and outburst, calling him a “filthy beast” and sending him on his quest to avenge his honor throughout the play.
Mildred's Aunt
Mildred's very reluctant chaperone on her trip to England, she finds her niece to be a poser.
Second Engineer
He takes Mildred down to the stokehole, though he is clearly very uncomfortable with her excursion. He feels intimidated by her higher class.
Guard
A prison guard at Blackwell prison, he tells the prisoners to keep quiet, and when Yank starts yelling, he hoses him.
Secretary of the I.W.W.
He is the primary representative for the International Workers of the World, O’Neill’s general example of a worker’s union. As he listens to Yank’s understanding of what the organization does, he becomes convinced rivals, in an attempt to mock or else spy on the union, have sent Yank rather than Yank coming of his own volition.
Stokers/Firemen
Workers in the stokehole on the ocean liner, they seem to be sheep easily led by whoever is the strongest leader of the pack, usually Yank. They often tease other members of their crew in unison, which makes their voices take on a “brazen, metallic quality” as if their throats were gramophones.
Ladies and Gentlemen of Fifth Avenue
Citizens of the Upper Class, they are consumed by their own greed and materialism, completely blocking out anything that is not of their kind, like Yank. They only notice Yank when he becomes an obstacle to them living the life they are accustomed and are quick to remove him forcibly when this happens.
