Supply chain issues are a growing concern for public sector emergency managers because communities rely on these privately-owned and operated systems to deliver goods needed for daily life and survival. Recent events have highlighted the many ways supply chains can be disrupted. Knowing how these systems are configured and how they operate is essential to making more effective operational decisions during emergencies and to support supply chain owners/operators restore flow following a disruption. Mapping the supply chain is a proven private sector practice for gaining visibility into these systems that may have application in the public sector. This paper describes why mapping helps improve emergency preparedness, how mapping has been done, and two case studies of its application for lifeline commodity supply chains in the National Capital Region. The paper concludes with a path forward for emergency managers seeking to use mapping to strengthen supply chain resilience in their communities, regardless of scale.