I was driving on Hiway 49 in the foothills and there were a LOT of Jefferson State flags, as you say.
There use to be a lot more but penryn, lincoln, newcastle, and auburn are being inundated with bay area transplants. They are driving up all the land values and destroying all the small town feeling.
I grew up in Sacramento and we kids used to spend a LOT of time wandering around Placerville, Jackson, Auburn and Folsom Lake.
Heck, I worked on the Upper American River project out of Forest Hill.
In the early 1960’s we were always shooting our .22s around Folsom Lake...there were no homes there at all.
My wife grew up in Lincoln.
Quite the change from those days.