>>2841593legally any claim should be marked. So personally I just look for areas that aren't marked. The claimholder can't prosecute me if they didn't properly mark their claim, that's their entire job. Same with private property. If there's no fences or signs I assume it's free to prospect because if they don't want me there they're required by law to mark the boundaries.
if you want to be legal and respectful you can search for claims at the local BLM or USFS and search private property on the county assessor's map. However I just go by signs. No sign means I'm going to prospect it. It's literally the owner's job to place signs. They can't complain about trespass if they didn't put a sign or a fence. Also anyone too lazy to maintain signs and fences isn't going to catch me anyways, because they're not present on the property often enough to see me.
your area is entirely 100% claimed, just like my area. But I'd bet most of the claims aren't legally marked, so that's the owner's problem. They're required to mark claims if they don't want people panning on them.