What are some Southern Gothic literature traits?

The Southern Gothic style of literature has roots in the romantic and Gothic styles of literature that originated in Britain. This style of writing has certain identifiable characteristics, and one of them is that they are set in the southern part of the United States. This type of writing is filled with imagery and symbolism, which is another characteristic. 
The Gothic style was interested in the themes of decay and isolationism. Edgar Allan Poe is a good example of an American writer who uses this style. Southern Gothic style usually centers around a character who is different from the norm of society. The themes of Southern Gothic literature often explore how marginalized people are misunderstood and often shunned by society. Another common theme in this style is for innocence to be surrounded by corruption. 
In "Good Country People," Joy, who changes her name to Hulga, is the oddball, or misfit character. She is educated beyond everyone she encounters. She lost her leg in a hunting accident. She has no desire to fit into the norms of society by marrying and having children. A Bible salesman comes to their house, and at first, Hulga is unimpressed and suspicious of him. But like all good con-men, he finds a way to break down her defenses. She thinks he is simple and good, and she doesn't believe in what he's selling but thinks she might like to have his attention for a while. Here is a quote from when her opinion of him begins to change. 

"The girl looked at him almost tenderly. “You poor baby,” she murmured. “It's just as well you don't understand,” and she pulled him by the neck, facedown, against her. “We are all damned,” she said, “but some of us have taken off our blindfolds and see that there's nothing to see. It's a kind of salvation.”
 

In the end, Hulga is duped by the con-man, who wanted to collect oddities, like the glass eye he got from another woman and the artificial leg he was going to take from Hulga. She is shocked to find he's not just good country people.