01Whose land decides almost everything
On private land, with the owner's written permission, detecting is generally lawful and what you may keep is whatever the agreement says.
On federal land it is not. The Archaeological Resources Protection Act of 1979 makes it an offence to excavate or remove archaeological resources from federal land without a permit, and the National Park Service prohibits metal detecting in units of the National Park System altogether. That covers national parks, national battlefields, national monuments and most national forest and Bureau of Land Management ground.
On state, county and municipal land the rules are set state by state, and they differ sharply. Our state pages name the authority for each and link to it, because the authority is the only source worth trusting.
02The three things that are never yours
Human remains. If you uncover what may be human bone, stop, do not disturb it further, mark the spot, leave the land and call local law enforcement. Every state treats disturbing a grave as a crime.
Anything from a grave, marked or unmarked. Cemeteries, family plots and burial grounds are off limits whoever owns the field they sit in.
Native American human remains, funerary objects, sacred objects and objects of cultural patrimony. The Native American Graves Protection and Repatriation Act governs these on federal and tribal land, and many states extend similar protection to private land. They are reported, never kept and never sold.
03Battlefields
Ground fought over in the Revolution, the Civil War or any other conflict is archaeology, not a target field, and the great majority of it is federally protected. Where a battlefield sits on private land outside federal protection, treat it as a site: record where each item came from, keep the context, and talk to the state historic preservation office before you strip it.
04Record what you find
There is no national scheme to send it to, which is exactly why the recording matters. Log every find against the booking with a photograph and the spot it came from. Over a season that record is worth more than the objects, and it is the only reason a future archaeologist will be able to make anything of what you took out of the ground.
05Report the significant ones
If something looks genuinely old or genuinely important, contact the State Historic Preservation Office for that state. They are not there to confiscate it from private land. They are there to record it, and a recorded find is worth more, not less.
06The ordinary courtesies
Fill your holes. Take the trash. Show the landowner everything before you leave, whatever the agreement says you owe them. Do not post the location of productive private land publicly. The reason there is land to book at all is that landowners trust the people who turn up.