Re: mid 1800's homesteads
pawinground, torrero is right. You'd be surprised how many spots were hit in yesteryear (whether or not the current owners knows or remembers). This is especially true if you're in a geographic zone where there were no shortage of md'rs in the '70s, '80s, '90s and '00s. If you put a bunch of good hunters in any area of the USA, and they do their homework (study old maps, history books, talk to old-timers, etc...) they will find and hunt sites.
Let me give you an example:
1) In the mid 1970s, as a young teenager, I took my trusty Whites 66TR to an old home, and knocked on the door. An elderly man told me "sure, go ahead". I got some clad, and a few wheats (the machine didn't reach that deep).
2) A few years later, in the late 1970s, I was the proud owner of a TR discriminator (ground breaking for their time!). I wanted to try some spots, to compare it to my older machine, so I purposefully went to places where I could compare to what I knew I'd already worked. So I went to that same old house. This time an elderly lady answered the door (apparently the wife of the elderly man who'd answered a few years earlier). She said "Go ahead, no one's ever hunted it before" (I didn't bother correcting her). I got a few more clad, and a few more oldies.
3) Flash forward to the very early 1980s, and I was the proud owner of a fast sweep VLF discriminator (ground breaking for their time!). Again, I wanted to see how it stacked up to my old machines, so again, I took it to that same home. This time, a young lady answers the door. She says "go ahead, we're liquidating our mom & dad's estate, since we've put them in a rest home. I'm sure they won't mind. And you might do good, since no one's ever detected here before" Doh! (In her mind, I suppose "mom and dad would have told me if anyone ever tried that here", eh?) This time I found two more oldies.
4) Flash forward to when I got my explorer about 5 yrs. ago. Again I wanted to try it at a place where I figured I'd totally worked it out, to see how it compared. Again I went to that SAME house. This time a man answered the door (the latest owner). He says "sure, go ahead. No one's ever done that here before" Doh! (btw, I didn't get anything else old this time, haha)
See how that works? There's just so many ways that the current owner will insist "no one's ever hunted this before", but they just don't know. Perhaps a renter from decades ago said "go ahead". Or perhaps the ranch foreman a decade or two ago told his kid brother "go ahead". Or quite frankly, perhaps people just did it, and didn't ask.