This is an interesting question as often in pieces of literature the mood or feeling that a text creates varies as the plot progresses. This excellent short story is no exception. Note how the mood starts off by giving us a sense of the hardship and misery of Tom Walker through the use of such words as "forlorn," "alone," and "straggling." However, very quickly the mood changes to one of foreboding or oppression as Tom Walker voyages into the swamp:
Like most shortcuts, it was an ill-chosen route. The swamp was thickly grown with great gloomy pines and hemlocks, some of them ninety feet high, which made it dark at noonday, and a retreat for all the owls of the neighbourhood. It was full of pits and quagmires, partly covered with weeds and mosses, where the green surface often betrayed the traveller into a gulf of black, smothering mud...
Notice how the description and diction create this mood of fear and unseen danger.
You might want to consider how the mood continues to develop throughout the story, for example when Tom starts his work as a banker and lives a civilised life, away from the supernatural images of the swamp. However, I think the mood that dominates is one of supernatural terror and fear.