National security law scholarship tends to focus on the balancing of security and liberty, and the overwhelming bulk of that scholarship is about such balancing on the horizontal axis among branches at the federal level. This Article challenges that standard focus by supplementing it with an account of the vertical axis and the emergent, post-9/11 role of state and local government in American national security law and policy. It argues for a federalism frame that emphasizes vertical intergovernmental arrangements for promoting and mediating a dense array of policy values over the long term. This federalism frame helps in understanding the cooperation and tension between the federal and local governments with respect to counterterrorism and national security intelligence, and also yields insights to guide reform of those relationships. The Article emphasizes two important values that have been neglected in the sparse scholarship on local government and national security functions: (1) accountability and the ways vertical intergovernmental arrangements enhance or degrade it, and (2) efficiency and the ways those arrangements promote public policy effectiveness. This Article reveals the important policy benefits of our shared federal-local national security system, and it suggests ways to better capture these benefits, especially if terrorism threats evolve to include a greater domestic component.