What is the setting of "An Occurrence at Owl Creek Bridge"?
Generally speaking, the setting of a story is the time and physical location.
The text of "An Occurrence at Owl Creek Bridge" never gives an actual date to the story. The reader is able to know that the story must be taking place between April 1861 and April 1865, because those are the dates of the American Civil War. Interestingly enough, Bierce's original text opened the story by stating that it took place during the summer of 1862.
As for the physical location of the events in the story, the reader is told that the story happens in northern Alabama.
A man stood upon a railroad bridge in northern Alabama, looking down into the swift water twenty feet below.
As the story continues, the reader learns that the bridge that Farquhar is standing on is a relatively short distance away from his plantation. In part two of the story, the Federal scout tells Farquhar that Owl Creek Bridge is "about thirty miles" from the house.
"How far is it to the Owl Creek bridge?" Farquhar asked.
"About thirty miles."