This brief describes the Girl RosterTM, a practical tool designed by the Population Council to help practitioners understand their program areas and elicit foundational information to intentionally link girls—especially highly marginalized adolescent girls—to the vital resources, facilities, and services to which they are entitled but often have limited or no access. The tool is a user-friendly, efficient, and cost-effective way to collect program-relevant information about girls in a community, using a mobile phone–based questionnaire (or, where resources do not permit, paper and pencil). The tool enables users to see a fuller view of girls’ lived realities in defined program areas, comprised of easily walkable or travelable communities.