Bill

I live not far from you and have encountered that same or similar style of construction. I don't know what it might be called or if it really has a name. It is not balloon framing, which is a style of stick (2x4) framing where the studs run from bottom plate on the first floor through to the top plate of the second. The second floor framing was hung from either a let in rim or onto a let in ledger. The type of building you have is I believe a folk style born of necessity and available materials.
Remember that at the time Mr. Grugan moved here this area was still fairly primitive. Wa. became a state the same year. The railroads had just built all over the area and it was booming. If you look at photos of the area at that time what you see commonly is stumps and spindly leftovers from the extensive logging that had been taking place.
My bet is that your “planking” is West Red Cedar. West. Red cedar was at one time considered a “junk” wood. Not that people were unaware of its rot resistant properties but the Fir was worth much more and if you were going to go to the work of cutting, bucking, skidding and shipping a tree at that time you went for the best paying tree. Not that that has changed

So, here is my theory. Most of the good timber had been cut, milled and was gone or in such high demand that it was priced at a premium. Mr. Grugan being a working guy may not have had the wherewithal to build a good balloon frame house (the more common technology) and he may have been a “boomer” with no plans to stay for any length of time. He was foreman at the mill and may have had access to a cheap (free?) material that allowed him to build what he could afford.
The chimney is I think another clue that this was built by someone on a tight budget. I have seen that detail before as well and believe it to be a cost saving measure.

It may be interesting to contact the history museum in Tacoma to see if they have any information for you and they might find your story interesting in that you have some history of the builder. I would be very interested to hear about whatever you learn.

J.E.B.