This document discusses using geographic data and interactive maps to identify populations remaining eligible for health insurance coverage. It finds that while smaller geographic areas like ZIP codes provide more neighborhood variation, larger areas like counties are more reliable. Combining census data on eligible populations with administrative enrollment records allows mapping the number and share of people still eligible by location. Interactive maps that include addresses of outreach sites, hospitals and other places can help target remaining eligible individuals. In sum, geographic data and interactive maps are useful tools to improve marketplace outreach when considering the tradeoffs of different geography levels.