The federally funded Cities Readiness Initiative (CRI) requires seamless federal, state, and local public health coordination to provide antibiotics to an entire city population within 48 hours of an aerosolized release of anthrax. We document practical lessons learned from the development and implementation of the Boston CRI plan. Key themes center on heightened emphasis on security, a new mass protection model of dispensing, neighborhood-centric clinic site selection, online training of Medical Reserve Corps volunteers, and the testing of operations through drills and exercises. Sharing such lessons can build national preparedness.