This novel takes place in the Manhattan neighborhood of Washington Square in the mid-nineteenth century. Washington Square begins with a portrait of Dr. Austin Sloper, a respectable physician. His wife, Catherine, gives birth to as on who dies at the age of three. Two years later, Catherine gives birth to a daughter named Catherine - but the childbirth is difficulty and the mother dies. The daughter, Catherine, is the heroine of the novel.
Dr. Sloper is almost immediately disappointed in Catherine. From the start, he views his daughter as a strange genetic twist of fate: she is not a boy; she is not beautiful like her mother; she is not clever like her father.
Dr. Sloper has two sister, both younger and both very different from each other. Dr. Sloper's favorite is Elizabeth who has married a merchant named Almond. Mrs. Almond is prudent and kind and throughout the novel she gives Dr. Sloper some good advice that he unfortunately discards. The other sister is Lavinia, a widow once married to an impoverished clergyman named Penniman. When Catherine is a few years old, Aunt Penniman comes to live in the Sloper household. Dr. Sloper finds his sister Lavinia to be excessively imaginative, unrealistic, and melodramatic. Nonetheless, Dr. Sloper thinks that Lavinia - as she is the girl's aunt - would be a good surrogate mother for Catherine.
Quickly, the novel moves forward to Catherine's late adolescence and early adulthood. Dr. Sloper remains decidedly disappointed in his dull, boring, plain-faced daughter. Though Sloper never explicitly says this to Catherine., Sloper's dismissive and sarcastic air really stunts Catherine's intellectual and emotional growth. Sloper expects little form Catherine and, for the most part, this is a self-fulfilling prophecy.
Marian, one of Aunt Almond's daughters, has become engaged to a man named Arthur Townsend. At Marian's engagement party, Catherine meets Morris Townsend, a smooth-talking and very good looking young man. He is a far-flung cousin of Arthur's, and has been traveling the world. Hence, Morris is a stranger in polite New York society.
At this same party, Morris meets aunt Lavinia and, seizing the opportunity, he tells her that he very much enjoyed his conversation with Catherine. In the days that follow, Aunt Lavinia plays the role of a meddling middleman. In his successive visits to the Sloper home, Morris becomes a cause of concern for Dr. Sloper. The doctor sees through Morris: a lazy charmer who has identified Catherine as the source of his fortune. At the same time, Aunt Lavinia does such a good job of sparking up a romance between Catherine and Morris that Catherine comes to believe that Morris does love her. Though Morris' primary motivation is economic, he is kind to Catherine and he treats her with far more love and consideration than Dr. Sloper does. Consequently, Dr. Sloper finds it difficult to pry Catherine away from Morris.
Dr. Sloper realizes that he cannot literally impose his will on Catherine and enforce any sort of restriction. Dr. Sloper can rely upon fear and threats, however. Sloper cannot withhold Catherine's inheritance left to her from her mother, but the doctor vows that if Catherine marries Morris, he will disown her as his daughter. This poses a concern form Morris because Catherine is only half as attractive if she comes with only her maternal fortune and not Dr. Sloper's.
When it seems that Catherine will remain defiant, Dr. Sloper asks her to postpone her plans and accompany him on a trip to Europe. Sloper hopes that he separation will split the couple. After six months, Catherine remains firm in her intent, so the doctor extends the trip for another six months, but this proves ineffective. Left at home alone, Lavinia develops her own social circle and Morris Townsend is a regular guest at the Sloper home. Morris has not spent this time finding gainful employment, though he does concoct a story about suddenly becoming co-partner of a commodities firm. Catherine takes this as good news and she is eager to get married.
Realizing that Catherine will arrive with a seriously diminished fortune, Morris backs out of the marriage, cowardly. After a string of awkward encounters, Morris leaves town. Weeks later, he mails a five page letter from Philadelphia. Catherine reveals these details to no one, although it is not difficult to see that her heart has been broken. Dr. Sloper remains suspicious that Catherine is simply waiting for him to die so that she can marry Morris. When he is near death, Dr. Sloper asks Catherine to promise that she won't marry Morris but Catherine is so offended by the doctor's audacity that she stubbornly refuses to make any vow or commitment. In the end, Dr. Sloper dies in his folly, believing Catherine to be treacherous. He gives most of her inheritance to charity.
A few years after Sloper's death, Morris Townsend returns, having learned that Catherine has never married. Aunt Lavinia lets him into the house to meet Catherine and Catherine is visibly upset. She dismisses Townsend after a few minutes - it is clear that she does not love him at all. Morris thought that Catherine had been waiting for him all of these years - but he never made any contact with her, so why would she be waiting for him now? Catherine continues to live a spinster life and she is able to find value and take pleasure in her own personal hobbies and interests.