Benjamin Banneker: SW 9 Intermediate Boundary Stone - Credit: Wikimedia Commons
Benjamin Banneker: SW 9 Intermediate Boundary Stone, also known as an Intermediate Stone of the District of Columbia, is a surveyors' boundary marker stone. The stone is located on the original boundary of the District of Columbia (see: Boundary markers of the original District of Columbia and History of Washington, D.C.) The stone is now on the boundary of Arlington County, Virginia and the City of Falls Church. It is within the two jurisdiction's Benjamin Banneker Park at 6620 18th Street North, Arlington. Read more on Wikipedia
Source: en.wikipedia.org