The Colour Out of Space
Specifically, Lovecraft was inspired by the cities and towns in Massachusetts. However, the specific location of Lovecraft Country is variable, as it was moved according to Lovecraft's literary needs. The location of Arkham was moved, as Lovecraft decided that it would have been destroyed by the Quabbin Reservoir, which was created to supply Boston with fresh water. This is alluded to in "The Colour Out of Space", as the "blasted heath" is submerged by the creation of a fictionalized version of the reservoir.