[chiph]

That happened to my parents when they went to sell their house. A neighbor had built a stone wall many years previously and it turned out to be a foot onto their land. The neighbor had to either tear down the wall, or buy ~140 square feet of land from mom & dad - and do it quickly, as it was holding up the sale. Then they had to get it resurveyed so the legal description reflected the new size.

Something I found out just now is that the original 13 colonies (the states on the east coast of the US other than Florida) use the "Metes and Bounds" system of surveying land. While the other 37 states use the PLSS - Public Land Survey System. Under Metes and Bounds a piece of land is described by its natural boundaries. Such as: "BEGINNING at the survey marker numbered 12345, thence North 19°32'14.24" for 148 feet, thence East at 104°0'23.75" to the Oak Tree, thence South", etc. where the segments join to form the boundary.

https://emilms.fema.gov/IS1120/groups/77.html