You chop down trees in your neighbor's yard. You fence in the area. For 20 years you walk your dog there. The neighbor watches and does nothing. After 20 years, you own the land, true or false?
It's not easy. But, under the legal principle of "adverse possession," people encroaching on land that is not theirs can become rightful owners if the actual owner sleeps on his or her rights.
Don't try this at home. And, state law prevents such claims against government or railroad land. But, it does happen. Adverse possession is rare. If you're the one claiming this right you have to be open about it, you can't slink over after dark. Your use must be exclusive. The rightful owner instructs you even once to 'get off my land,' and the exclusive element is gone and you start over again.
Your claim has to be continuous, meaning you don't stop what you're doing and take breaks. Your use must be adverse to the property owner, meaning that your use is inconsistent with his or her ownership. You do not seek the landowner's permission.
Finally, the actual owner needs to be on notice. You can't lurk in the background.
All of these elements must continue uninterrupted for a time period set by statute in each state, 20 years in Massachusetts and New Hampshire, but shorter in some states.
Courts often reject adverse possession claims.
Before buying property, determine exactly where the boundary lines are. This is simple in a suburban cookie cutter lot. But, not so easy where the boundaries are ambiguous, running through woods and wetlands. Make sure the lot lines are clearly identified and that there are no 'squatters.'
Some landowners annually walk their boundary lines even forging through rough terrain. Not a bad idea. The owner shatters the exclusivity and continuity required to establish an adverse possession claim.