Don -
Connecting Girt framing did begin here in New England, Northern NE at that. And as I alluded to upthread, such framing seems to have been pretty much limited to Maine & NH, though I can not say for certain how common it might be represented on the west bank of the Conneticutt. I do know that the southern extent of the regional dominance it holds, stops almost dead on, the Mass/NH line. (I came up in a Merrimack Valley border town) Paradoxically, this seems to be the same range of geographic dominance in which, can be found, common purlins.
Neither stytem of framing seems to historically have spread beyond this regional range. I have long tried to research first, what influence/s drove to dominance common pulin roof systems (assuming some regional variation in Olde England played in - this seems not to be the case) And then, what might have influenced a region wide "paridigm" shift in framing. The change was abrupt, like the flipping of a switch, and I know of no other like it (I have been in but one building I would call transitional - having both jowled posts and CG's - and at the same time having seen numerous iterations of "transitional" stick buildings) The only other such related and rapid shift, I know of, was the one abandoning scribe and accepting Square Rule, though in its case the shift was not region bound, but continental in scope, but every bit as rapid. I know of no other area where the plate system was abandoned.
To answer your followup - Almost ironically, Yes, current framers work with these systems today. This largly due to authors from and influenced by this home region, having penned well read books which went on to heavily influence the timber framing revival.
And to speak to the sawmill side of this thread - Frames with the amount of hewing I describe above, are in my expierience, something of a rarity, NE seemingly blessed with good water (Horsepower producing head) saw the building of mills from early on, at least match, or (with intent) better the rate of the spread of settlement - The well heeled and connected granted the best mill sites -
This book/link suggests just how early -
http://books.google.com/books?id=MxILAAAAIAAJ&pg=PA6&lpg=PA6&dq
