This article addresses the interplay of two old Missouri property law doctrines:  The doctrine of adverse possession and the doctrine of boundary by acquiescence.          
You are probably familiar with the doctrine of adverse possession, where an adverse possessor claims legal title in certain property (often called the “disputed area”) because his possession of such land has been hostile and under a claim of right, actual, open and notorious, exclusive and continuous for 10 years or more. This doctrine presupposes that an adverse possessor does not have an agreement with the true owner to use the disputed area, such as a lease agreement, but that he possesses the area because he believes it to be his own.    
But what if there is an actual agreement between adjacent property owners establishing a certain boundary (such as a fence or tree line) because neither knows the exact location of the true boundary line?      
The doctrine of boundary by acquiescence then comes into play. It establishes a boundary when there is some contention as to the location of the true boundary line. Acquiescence may be proven by written agreement or by acts and conduct of the adjacent owners showing long acquiescence to the use of a certain boundary.  
Together, these doctrines state that once an express agreement or acquiescence to a boundary line has been proven, possession from that date forward becomes adverse and the 10-year period for adverse possession begins to run.  
Let’s see how these doctrines play out in a hypothetical situation. Lawyer purchases 10 acres next to Rancher, who owns 40 acres. An old fence generally separates the properties, but neither party has ever had his parcel surveyed. There is no written agreement between the parties, but Lawyer uses one side of the fence for activities such as lawn mowing, landscaping and playing with his kids, while Rancher uses the other side of the fence for activities such as raising livestock and baling hay. Neither attempts to use the other side of the fence or prohibit the other owner from using the other side of the fence. Fifteen years pass by and Rancher commissions a survey, which reveals that the fence, in actuality, is fifty (50) feet on his own property. Rancher tells Lawyer he is going to move the fence to the true property line and prohibit Lawyer from further using the disputed area. Lawyer objects and claims the disputed parcel as his own.
Under this situation, if the parties did not acquiesce to the use of the fence line, then Lawyer’s possession of the disputed area was adverse from the beginning and he will be entitled to the land after 10 years. If, however, the parties did acquiesce to the fence line, Lawyer’s possession becomes adverse only when the boundary becomes fixed. Until then, his use of the disputed land is said to be by agreement.  
So, how long does it take to establish or fix a boundary by acquiescence where there is no written agreement?  The answer is likely several years.  Thus, the longer it takes to establish the boundary through acquiescence, the longer it will take for the adverse possessor to show he is entitled to the disputed area by adverse possession.  Under our hypo, 15 years would be more than enough time to show adverse possession alone, but if the parties agreed to use the fence line as the boundary, 15 years may not be enough time to show acquiescence and adverse possession.
Jerry W. Potocnik is an attorney in Blue Springs, Mo. He is licensed to practice law in Missouri and Kansas.


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