Is there somewhere that it's labeled a "Historic site" ? As in a plaque, a marker, or a trinomial system archie designation, etc....?
Or are
you one saying that it's a "historic site" ? Simply because it's an old spot ?
Because, when you think of it : Anytime you see someone here posting show & tell of old coins, old relics, old tokens, etc.... Then
*by definition*, they must have been hunting a "historic site".
I mean: No one finds seateds, reales, LC's, gold coins, relics, in "modern sites", right ? They are finding them in sites that have historical usage. Right ? Lest they could never have found the old coins, IN THE FIRST PLACE , if they hadn't been hunting "a historic site".
Thus yes, we all detect historic sites.
But If you meant: "Historic sites that are off-limits", and hence : "How do I know ?", then here's how you can know :
You look up the rules and laws , for the site in question. Eg.: Dogs on leash, no fireworks, closes at dusk, etc.... If you see nothing that says "No md'ing", then presto, it's not prohibited.
HOWEVER, we all use a bit of common sense. If it's an obvious historic themed monument (and not just simply "an old park" or "an old train station"), then sure, don't be an eyesore at such places, even in the absence of a specific rule or law.