
This map is a copy of the 1971 Great Kingdom Map given to Dave Megarry by Dave Arneson at some point in the mid-70s. Megarry recently uncovered it in his files.
A previous version of the same map was shown in a video by Jon Peterson (Playing at the World) a few years ago.
This post has my compiled notes comparing this map to the published WoG Folio setting, and the setting details mentioned in the novel Quag Keep (which Andre Norton wrote based on notes from Gygax):
Megarry's Copy of the Great Kingdom Map
I struggled over whether to place this in the Blackmoor or Greyhawk setting forum here, since it really it shows a time period when the two settings were one! I decided to place it here since most of the linked post is dedicated to comparison with the later Greyhawk setting, which I am more familiar with than Blackmoor.
If you are wondering where the City of Greyhawk is on this map, it isn't shown because presumably it hadn't been created when this map was drawn - and also this map doesn't really indicate cities. It would most likely be located near the south corner of the Nyr Dyv, slightly up river.