What does the story say about the nature of marriage?

Kate Chopin's "The Story of an Hour" indicates that marriage can make partners, particularly women, feel constrained and oppressed.
In the story, Louise Mallard gets the tragic news that her husband, Brently, has been killed in a train accident. Louise has "heart trouble," so her family must break the news gently, and once they do, she weeps and then retreats to her room. Once she is in the room alone, she realizes that her husband's death, while sad, also ensures her freedom. Louise looks out the window and begins to notice the world outside:

She could see in the open square before her house the tops of trees that were all aquiver with the new spring life.

This description parallels Louise's epiphany, which is soon to follow, that her husband's death is also her own rebirth. She begins to feel strange, as

There was something coming to her and she was waiting for it, fearfully. What was it? She did not know; it was too subtle and elusive to name. But she felt it, creeping out of the sky, reaching toward her through the sounds, the scents, the color that filled the air.

The life of the world outside her window has now infiltrated her senses and her room. Her mind is gradually becoming aware of the independence her husband's death will provide her. When she finally is able to articulate the feeling that is, in the previous quote, "too subtle and elusive to name," she exclaims, "'Free! Body and soul free!"
Louise Mallard admits that she will mourn her husband and will cry at his funeral. However, she also understands now the ways in which marriage as an institution has held her back. She reflects,

There would be no one to live for during those coming years; she would live for herself. There would be no powerful will bending hers in that blind persistence with which men and women believe they have a right to impose a private will upon a fellow-creature. A kind intention or a cruel intention made the act seem no less a crime as she looked upon it in that brief moment of illumination.

In this important passage, Louise criticizes marriage rather than her husband as an individual. She believes in this moment that marriage makes her will subordinate to that of her husband, and she labels that "a crime." In other words, Louise has come to realize that a woman has no real independence in marriage and must always serve another's needs. Instead, "she would live for herself." Louise is excited by this potential as she leaves her room and "carried herself unwittingly like a goddess of Victory" to the stairs. Sadly, her exhilaration will be short-lived, as Brently walks through the door very much alive, and the shock results in Louise's death by heart attack. While the observers say she died of "the joy that kills," the readers know she dies not of happiness but of extreme disappointment: that free future she just dreamed of for herself will never be hers as soon as her husband returns to the house.