And Ed actually tried to keep being too influenced by historical places to a minimum on purpose btw, it was conscious choice. It's the influence of others like Jeff Grubb, Douglas Niles, and others that certain regions like Mulhorand are so heavily inspired by Ancient Egypt (although I have argued that in the past it's really more like Ptolemy Egypt IMHO) and other historical locations (Moonshae Isles=Celtic/Arthorian Legend, Zakhara/Al Qadim=Islamic Golden Age with touches of preIslamic Arabia, Unther=Mesopotiumia/Canaan, ect...).
Well, not so much. Ed did create most of the Realms. Ed's focus was always on his favorate areas; the areas his players where based in: the North, The Heartlands and the Dalelands. Ed, being Ed, did make up much of the rest of the world, but often in just a reference paragraph or two. Still, that laid out a lot of ground work.. And when the others came in, they did often work with Ed or at least go off his massive pile of notes.