Edgar Allan Poe's short stories are predominantly classified as "Gothic" literature. But, what is it that makes them Gothic stories? Mostly, they fulfil the following "requirements". They are usually set in a tone that is very gloomy, dark, and threatening. Then, the events in his stories are also usually very strange, melodramatic, and lead to something evil. There is always an eerie atmosphere and a twist in the plot.
The Fall of the House of Usher was printed in his 1840 edition of Tales of the Grotesque and Arabesque - a term also used in that specific story. All the stories in the collection can be divided into two categories. Either Grotesque or Arabesque. The Arabesque category - which the Fall of the House of Usher is part of - contained stories that involve very few people(Roderick, Madeline and the Narrator), strange ideas and plot twists; and are set in abstract locations(The decaying House of Usher). If one takes into account that both Grotesque and Arabesque are terms mostly used to define works of art - arabesque being art that involves many interlaced and complex geometric patterns - one can see how the story fits perfectly into the category.
There are also many terms and images in the story that, classically, form part of the Gothic genre. The first thing that one notices is how gloomy and still everything is, clearly playing along with the Gothic genre. But the one of the most important giveaways however is the setting; The House of Usher. It fits the perfect description of a classic haunted house where supernatural things may occur. There is also the connection that Roderick makes between his illness and the house as a possible cause. This connection also continues when one is told that when people speak of the House of Usher they refer, physically, to the house, but also figuratively, to the Usher family. Now one can see how the decaying physical integrity of the House is reflected in Roderick's health.