Stone walls

While the foundation work is going on, our contractor did some test holes on the main part of the house.  We'll be breaking through this wall in a couple of places, so he wanted to see what we'd be dealing with...

He was quite surprised to find that behind the clapboards, the walls are stone!

Here's a peak...

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It now makes sense why the electrician was having so much trouble trying to install an outlet in our bedroom and said that it was too obstructed to run the lines inside that exterior wall!

I want to find out if the house was originally stone, or if this was some kind of common building practice for the time?  The walls aren't as thick as the basement/foundation stone walls- which if they were meant to be structural, I'd think they'd have been thick all the way up.

I'm anxious for them to take down the rest of the clapboards from the back so we can see how it was constructed!  We asked the builder if it would be possible to leave them once the clapboards are off.   I'm thinking it might look really cool to have the exposed stone for the back entryway/mudroom wall.  He said it will depend on what kind of shape the rocks & mortar is in, so we'll see!