You should probably check for "public land", which is found in almost all States but is very, very frequent west of Texas. See e.g. the map at:

https://vividmaps.com/non-private-land-in-united-states/

But you should check what you can do in it. It will be probably legal to park a vehicle there and very probably illegal to dig a moat around it (public means "of everyone", not just "free").

Why would someone who rejects society care about society's laws?