Abjuring a national police force, the United States relies instead on a decentralized network of federal, state, and local law enforcement agencies to fight crime, including the modern threat of terrorism. The FBI has primary jurisdiction for all domestic counterterrorism investigations and intelligence operations, but the USA PATRIOT Act and other post-9/11 homeland security measures emphasize the need for sharing national security intelligence information among agencies at all levels as full partners. This quest has been hampered by controversy and challenges of all sorts—a situation not unprecedented in American history. Following the premise that history may provide useful lessons for the present, this paper examines the roles and relationships among federal, state and local law enforcement agencies in domestic intelligence operations relating to national security during a succession of crises, from World War I to the current War on Terror. An apparent pattern emerges in which agencies at all levels mobilize with widespread public, legislative and judicial support during times of war or domestic crisis in an effort to coordinate domestic intelligence operations, but are later forced to alter or scuttle the operations in the face of legal challenges, bureaucratic rivalries, and waning public support in peacetime.