Geocaching is something that Jim and I have dabbled in a bit. We live near the Natchez Trace Parkway (in Tennessee), and have found a couple of hidden caches around there, and we plan to hide a few near there as well.

Apparently there is some controversy as to whether or not caches can be placed on property within the Natchez Trace Parkway or not. Technically, state parks are fair game, and are NOT off limits for geocaching. Whereas, national parks are, in fact, OFF LIMITS for geocaching.

That said, according to Pater47:

Yes, the Natchez Trace Parkway is indeed a National Park and is officially off-limits. That being said, there are a few along the trace within park bounds and many more just outside park bounds.

And seconded by Mtn-Man:

This is correct. Officially, they are not allowed there unless you get permission. In some areas, they will allow them.