Why is the farm important to the story in E. B. White's Charlotte's Web?

The farm is the main setting for the novel Charlotte's Web. It is there that Wilbur faces his trials and is saved by various characters. Interestingly, both of Wilbur's "saviors" are female characters. Wilbur is first saved by the young girl Fern, who sends him to Zuckerman's farm. Wilbur meets a variety of characters at the farm, some helpful and some sneaky. Most notably, the farm is where Wilbur meets his second savior, Charlotte the spider.
Since Wilbur is getting bigger, he will soon be slaughtered for food. Therefore, the farm not only serves as a setting, but as a sort of antagonist for Wilbur. It started out as a happy home, but eventually became almost a prison for Wilbur. At the farm, there is no escape from his ultimate fate. The farm does become safe again when Charlotte steps in with her webs to save Wilbur.  
The farm is important because it is the setting and has a dual symbolism: home and prison.