Hagerstown anchors the Hagerstown-Martinsburg , MD-WV Metropolitan Statistical Area , which lies just northwest of the Washington-Baltimore-Northern Virginia , DC-MD-VA-WV Combined Statistical Area in the Great Appalachian Valley . Hagerstown anchors the Hagerstown-Martinsburg , MD-WV Metropolitan Statistical Area , which lies just northwest of the Washington-Baltimore-Northern Virginia , DC-MD-VA-WV Combined Statistical Area in the heart of the Great Appalachian Valley .