Under current Washington law, initially enacted in 1854, if a third party has used a piece of land for ten years, he or she may bring an action to acquire title to that property. The use of the land must be actual, open and notorious, hostile, uninterrupted and exclusive. In short, the use must give the landowner notice that someone is using the land and that the level of use must be consistent with the nature and locale of the land. The state of mind of the adverse possessor is not relevant to the action to acquire title. Adverse possession can only occur between private parties.
Exceptions exist for landowners who are incapacitated.
Washington State has enacted statutes to protect specialized landowners, such as owners of timber lands. A typical modern day adverse possession case involves a boundary line dispute where a neighbor has built a structure or fence over the boundary line. It has been suggested that landowners in rural areas are losing parts of their land through adverse possession due to the actions of unscrupulous neighbors. As a result, these landowners have had the value of their land diminished due to the requirements of the Growth Management Act. The common law requirements for adverse possession are codified.