duty at any given time. The administrative facilities for both guard forces are located within the JSA. Layout While the boundary has remained the same over the years, the buildings themselves have changed. Some have been removed, including all of the KPA checkpoints on the southern half of the JSA. New buildings have been constructed, whilst some existing buildings have been expanded or simply renovated. The only boundary change of the Joint Security Area was the enforcement of the dividing line within the JSA after the murders of two American officers in 1976. Prior to this, the entire area was neutral, where members of either side possessed the freedom of movement within the JSA. Since the enforcement of the Military Demarcation Line (MDL) within the JSA, several UNC checkpoint buildings have also been rebuilt and/or renamed as well. Examples of this are what was called Observation Post (OP) No. 5 on the hill overlooking the Bridge of No Return, is now Checkpoint (CP) #3, while what used to be called CP#3 (and sometimes called "The Loneliest Outpost in the World") was the UNC checkpoint at the southern end of the Bridge of No Return. After the enforcement of the MDL, the North no longer had a road leading into the JSA, and within three days they built what is now known as the "72-Hour Bridge" or "Bridge of 72 Hours". Landmarks North Phanmun Pavilion Unification Pavilion South Freedom House Peace House Neutral or Joint T1 through T3 United Nations Command staffing The United Nations Command Security Battalion—Joint Security Area was constituted on May 5, 1952, as Army Unit 8020, United Nations Command Military Armistice Commission Support Group (Provisional). Originally authorized five officers and ten enlisted soldiers, the unit grew to over 1,400 officers and men supporting almost 32,000 soldiers, civilians, and diplomats involved in negotiating and then enforcing the Armistice Agreement. By the end of February 1954 the scope of work declined and the number of soldiers assigned to the unit declined as well. For the next 50 years, the unit underwent several organizational and name changes, although the original mission to secure the Joint Security Area remains the same today as it was in 1952. On June 11, 1979, the name was changed from US Army Support Group (Joint Security Area) to United Nations Command Support Group—Joint Security Area, and further changed to United Nations Command Security Force—Joint Security