Sour Cream raisin pie

I love sour cream raisin pie!
First and most importantly, you gotta good recipe?
Secondly, I'm interested regarding this delights origin.
My curiousity began about 15 yrs. ago when I motorcycled every free moment I had(41 of the 48 contigious states). I particularly enjoy the Rocky Mtn. states. I began noticing this dessert available at the "roadfood" stops I made. Most available in Montana, and both Dakotas it seemed, more extensively I'm sure.
As to origin, my romantic theory is, if a Pioneer had a milkcow, they would have sour cream. Back then, dried fruit was available, if you could afford. Just wondering????????