From the beginning, Fort Warren’s heart was the six-acre parade ground. When the Civil War broke out soon after the fort was completed, the area was still covered in construction debris, and newly enlisted Massachusetts regiments cleaned it up as they trained. To increase morale, they sang as they worked and eventually came up with the famous lyrics for “John Brown’s Body.” Since that time the parade ground has been used for drills, inspection, parades, and calisthenics, as well as off-duty sports such as baseball and football. The oldest maples and horse chestnuts on the perimeter date back to the 1880s. Soldiers drilled there in the early morning during the Second World War, with the fort’s Front II, the northernmost of the five interior walls, in the background.