During the Civil War, the U.S. Army constructed a series of forts and artillery batteries around Washington to protect it from Confederate attack. Forts O'Rourke, Weed, Farnsworth, and Lyon stood just to the north, and Fort Willard which still exists, to the east. These fortifications constituted the extreme southern defense line of the city. By the war's end, a line of 163 forts and batteries extended about 37 miles around Washington, but today only a handful survive. A century later, during the Cold War, a ring of Nike missile sites similarly encircled the capital to protect it.