Patching and Plastering - 5/8" Plasterboard in old cap cod??

I'm getting ready to remodel my kitchen and I need to get into the walls for insulation, electric, etc. I thought that I had plaster walls and lathing behind it, but it appears that I have a 5/8" plasterboard?? It doesn't appear to be drywall. It seems harder and definitely thicker... but no lathing or wire mesh. Any insight on what type of walls I have?

Forgive my ignorance, but I thought before drywall they only used a plaster/lathing combo. Thanks in advance.

Preservation Brief 21: Repairing Historic Flat Plaster--Walls and Ceilings (http://www.nps.gov/history/hps/tps/briefs/brief21.htm)
Be safe, Gary

How old is the house? on the newer homes with plaster they use blueboard with a plaster veneer. Have you torn enough of the wall down to know for sure what you have?

I looked in the crawlspace upstairs. I see no lathing. It can't be drywall.

If there isn't any type of lath - it would have to be drywall :confused:

But could it be gypsum plaster over gypsum lath?
If I had that I would go to great effort to preserve it.

After doing some research I believe it's blueboard with a plaster veneer. I plan to preserve it as much as possible, but I'm remodeling the kitchen and need to dig into the walls to route some electrical lines. No biggie since the cabs will cover the patches. I think I'm scrapping the blown in insulation idea and leaving it as-as.

Thanks for the comments.