Two centuries ago, when talk of witch-blood, Satan-worship, and strange forest presences was not laughed at, it was the custom to give reasons for avoiding the locality. In our sensible age - since the Dunwich horror of 1928 was hushed up by those who had the town's and the world's welfare at heart - people shun it without knowing exactly why.
-- Narrator (I paragraph 4)

Importance: This quote sets up the tense of the story. Through this quote we learn that the events of the Horror took place in the past. This also implies that the reason that the reader may have not heard of the incident is because the town covered it up.

I myself did not more than a Fortnight ago catch a very plain Discourse of evil Powers in the Hill behind my House; wherein there were a Rattling and Rolling, Groaning, Screeching, and Hissing, such as no Things of this Earth could...
-- Reverend Abijah Hoadley (I paragraph 6)