In "The Story of an Hour", Mrs. Mallard closes the door to her room so that Josephine cannot get in, yet she leaves the window open.
Why does Chopin make a point of telling the reader this? How might this relate to the idea of being "free" and to the implicit idea that she is somehow imprisoned?
In addition to the important detail of the window being open, however, Chopin is clear to say that the door in closed. No one can get in. The secret places in here heart are closed off as well, and she cannot and does not express her need for freedom to anyone. In addition, the closed door keeps her locked. She can dream by looking out the window, but she can not escape her life--she can not escape through that window. The only escape is closed. The ending reaffirms that her only escape from her life is death.
Leaving the window open certainly relates to Mrs. Mallard's freedom. If you read the passage again, she notices all of the wonderful things of life that are happening below, things she's never been a part of. It was only a short time ago that she prayed for her life to be short, and now she's praying for it to be long because she can now live the life she wants for herself, not the life of her husband. The window represents her freedom to be able to live her life now that her husband is dead. The open window is her invitation to live her life to the fullest, free of her husband's restrictions and free of her responsibilities as a wife. This is why she feels like a prisoner in the house.
Chopin wants us to know how women felt during this period of time. Mrs. Mallard says her husband never mistreated her, but she still feels imprisoned in the institution of marriage. She isn't free to express herself or to try things she's interested in. This point is really brought home in the ironic ending when Louise Mallard dies when she sees her husband is still alive. Although the others think she dies because she's so happy to see her husband is alive, she really dies because her freedom has lasted only a short time. She can't accept the fact that she has to go back to her old life and lose the dreams she had while sitting and looking out the window.