I don't know either. I live out in the boonies, so what might be ok out where I live might not be in other areas? I also live in Texas and we tend to be pretty tolerant around here. Unlikely to find people shooting at you for landing on their property.
You are, most likely, living under uncontrolled airspace, which generally means that a pilot may land his aircraft at his discretion with permission of the landowner. If the pilot has filed a flight plan, it is his responsibility to notify the FAA that he is down and safe, therby closing it, or closing that particular leg, if it is a stopover flight plan. An open flight plan that is not closed within a certain timeframe of filed ETA (I believe it's an hour)causes the authorities to begin a search.
Flying and landing in controlled airspace is a whole other matter, and generally depends on the airspace classification(B,C, or D) and floor the airspace begins at where the pilot intends to land as to whether the aircraft can be landed under normal operations with or without notification of the controlling authority (Tower/Air traffic Control/ FAA Regional Center).
A pilot can land his aircraft to the ground without permission at his discretion during an emergency or precautionary situation