The statutory time frame for adverse possession in Washington is generally 10 years (exceptions for having color of title, timberlands, paying taxes, etc.). If someone meets all the elements of adverse possession, the ownership of the land transfers to them automatically - though they would have to quiet title through the courts - or possibly a Boundary Line Agreement (RCW 58.04.007) to get 'legal' title. The adverse possessor has to prove all the elements of adverse possession...and you'll see these words as the elements: continueous, actual, open, notorious, etc....but, what they really mean is: Did the other owner use the property as if it was his own - and without the permission of the true owner - for the statutory period? Adverse possession is VERY common in Washington state - especially in less urban areas...like Stanwood (though I think one more Starbucks and Stanwood will be very urban!).