This report describes the Community Supervision Mapping System (CSMS), an online tool that enables users to map the formerly incarcerated and others on probation, along with related data such as service provider locations and police districts. CSMS was developed by The Providence Plan and piloted in Rhode Island in 2008. It was designed to be a user-friendly, low-cost software package that could be easily replicated in other jurisdictions. This report documents the mapping systems development and its implementation by probation officers and law enforcement, and includes a process and initial outcome evaluation. In addition, lessons learned are synthesized to offer guidance to jurisdictions seeking to adopt a geographically-informed approach to prisoner reentry.