 The Cold War led to the expansion of national defense government programs housed in offices in Northern Virginia near Washington , D.C. , and correlative population growth . The Central Intelligence Agency in Langley was involved in various Cold War events , including as the target of Soviet espionage activities . Also among the federal developments was the Pentagon , built during World War II as the headquarters for the Department of Defense . It was one of the targets of the September 11 attacks ; 189 people died at the site when a jet passenger plane was crashed into the building . 
