In the Gay Nineties, on New York's Bowery, known as the "livest mile on the face of the globe," Chuck Connors, the owner of a saloon which boasts the "largest schooner of beer," finds that his rival, Steve Brody, has thrown a mushmelon at his window. After the happy-go-lucky Steve explains that he threw the melon on a dare, Chuck is about to fight him when they learn of a fire in Chinatown. Both men call upon their volunteer fire brigades, and they wager $100 on which will be the first to throw water on the fire. Although Steve gets there first, he finds Chuck's young pal, Swipes McGurk, sitting on a barrel over the fire hydrant so that Chuck's brigade can use it first. The rival fire fighters get into a tremendous fight and soon lie scattered in the street and gutters as the fire reduces the building to a smoldering ruin. Steve vows to get even, but when two hoodlums, Slick and Googy from Jersey City, offer to kill Chuck for $500, Steve fights them. When Chuck becomes the manager of heavyweight prizefighter Bloody Butch, Steve bets Chuck $500 that his own fighter, whom he calls "The Masked Marvel," can beat him. After the "Marvel" knocks out Bloody Butch with one punch, he is revealed to be boxing legend John L. Sullivan. When Chuck sees a naïve girl, Lucy Calhoun, about to accept a proposition from Slick and Googy, he warns them not to "hawk" girls in his place. Lucy thanks Chuck and explains that she is homeless and looking for work. Chuck takes her to his apartment, where he lives with Swipes, and lets her sleep there. In the morning, he is pleasantly surprised, while Swipes is annoyed, to find that Lucy has cleaned up the place and cooked breakfast. Later, Chuck finds that Swipes has locked Lucy in a closet and spanks him. Humiliated before Lucy, Swipes packs and leaves. That night, Steve invites Swipes to move in with him. Steve then tries to make love with Lucy, thinking she is Chuck's mistress. She bites his hand, drawing blood, and after he apologizes, he asks if he can call on her. They soon fall in love, and Steve reveals his ambition to run a saloon bigger than Chuck's. When two brewers offer to back him if he can bring his name into prominence, Steve decides to jump off the Brooklyn Bridge as a stunt. After Chuck bets his saloon against a free burial that Steve won't make it alive, Steve gets a life-sized dummy made up to look like him and arranges for Swipes to throw it off the bridge at the time of the jump. As an estimated crowd of 100,000 gathers at the bridge, Swipes finds the dummy missing. Despite Swipes's pleas, Steve vows to make the jump anyway, so that no one can say he didn't take a dare. Meanwhile, Chuck tries to calm down Carrie Nation and her band of women, who have come to tear down his saloon with axes and hatchets. When he sees Steve lifted in a parade after making the jump, however, Chuck encourages the reformers to destroy the saloon, which they do. Steve soon opens the saloon again, and when war is declared against Spain, Chuck enlists to get away from the Bowery, where he is no longer a big shot. When he returns to his apartment to pack, he finds that Swipes has moved back. After Slick and Googy tell Chuck that Steve did not jump from the bridge and show him the dummy, Chuck demands his saloon back. Steve denies using the dummy, and they have a long fight on a barge in the river to settle their differences. After Chuck returns victorious, he is arrested for assault and battery with intent to kill. Steve, however, refuses to implicate him. In Steve's hospital room, he and Chuck begin another fight, but Swipes stops them and urges them to become friends. After they shake hands, Chuck dares Steve to join him in Cuba. At a parade for departing soldiers, Chuck tells Lucy to kiss Steve goodbye, and after she does, she also kisses Chuck. The men lament not being able to say goodbye to Swipes, but they soon see, to their delight, that he is hiding in an artillery box on the supply wagon just ahead of them.