Adverse possession—sometimes called squatter's rights—occurs when a person or entity who does not own a certain piece of real property occupies or uses it in a way that is adverse to the owner of the property—meaning the use is in conflict or at odds with the property owner’s interests.

If this adverse possession or use of the property meets the legal standard for adverse possession—often described as use that is continuous, exclusive, hostile, open, and notorious—and continues for the prescribed period of time (usually specified in the state statute)—the person or entity adversely possessing or using the property will acquire ownership of the property (title). This ownership will result in the changing of boundary lines.

Because the required adverse possession must be open, obvious, and adverse to the owner’s interests, title may only be acquired by adverse possession to the portion of property that is used in that way.

Adverse possession laws vary from state to state and may be located in a state’s court opinions (also known as common law or case law) or, more often, in its statutes.

In South Dakota, adverse possession laws are codified in state statutes. To claim ownership of property through adverse possession, the claimant must occupy the property in a manner that is continuous, exclusive, hostile, open, and notorious for a statutory period, which in South Dakota is 20 years (SDCL 15-3-1). The occupation must be such that it gives the true owner a cause of action for possession, meaning it must be obvious to the owner that someone is asserting a claim against their property. The claimant must treat the property as their own, to the exclusion of the true owner, and without permission from the owner. If all legal requirements are met over the continuous period of 20 years, the claimant may be able to acquire legal title to the property, potentially altering the boundary lines. It is important to note that adverse possession claims can be complex and fact-specific, and anyone considering or facing such a claim should consult with an attorney to understand their rights and obligations under South Dakota law.