My property in northern California was the site of a mine in the 1800s. The pits are still there along with the remains of some of the mine workings. I thought that was it, but while I was clearing some brush this weekend in an area I've rarely gone through, I found the collapsed remains of an adobe brick shack, complete with some old metal artifacts like pick heads and some stuff I can't identify. Kind of cool. I know - stuff that is maybe 150 years old isn't all that historical in most of the world, but it's pretty old for this part of the west.