Sam Hill was a real live person. He may not be the source of this expression but he was an early proponent of paved roads and highways in the early 20th century in the Pacific Northwest. His home is a museum and I’ve been in it. Actually a pretty interesting guy
“...but he was an early proponent of paved roads...”
My great-great grandfather lived along one of the first paved roads and would sit out on the front porch smoking his pipe. He said it was so nice to sit out there with no dust and the noise from the old bumpy road.
Often people would stop, roll down their windows and say “Hey mister - what the heck is going on with this road?” - never being on a paved road before.
My great-great grandfather would reply “Sam Hill!”
The TRUE story behind the origins of “What in the Sam Hill!?”
Disclaimer - my g-g-grandparents all lived in Norway.
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So the above story would have been spoken in Norwegian it seems.