In a 1934 letter to Rimel, Lovecraft remarks… “I didn’t get more than 100 miles from my home until I was 31 years old” (i.e. circa 1922), which provides a useful limit of what he might or might not have seen as a boy, if only from a passing train. No glimpse of the sinister and misty Catskills (“Lurking Fear”) from a Hudson Valley train, then, on a trip with his grandfather.
Drawing a 100 mile circle from his home does however suggest possible youthful visits to…
* the vicinity of Portsmouth and Rochester in the north, via Boston.
* north-west as far as the Berkshire Hills and the river-towns that lie to the east of them.
* south-west along the coast to New Haven.