The processes for implementing effective programs at scale in low-income countries have not been well-documented in the peer-reviewed literature. This article describes the initial steps taken by one such program—the BRAC Manoshi Project, which now reaches a population of 6.9 million. The project has achieved notable increases in facility births and reductions in maternal and neonatal mortality. The focus of the paper is on the initial steps—community engagement, social mapping, and census taking. Community engagement began with (1) engaging local leaders, (2) creating Maternal, Neonatal, and Child Health Committees for populations of approximately 10,000 people, (3) responding to advice from the community, (4) social mapping of the community, and (5) census taking. Social mapping involved community members working with BRAC staff to map all important physical features that affect how the community carries out its daily functions—such as alleys, lanes and roads, schools, mosques, markets, pharmacies, health facilities, latrine sites, and ponds. As the social mapping progressed, it became possible to conduct household censuses with maps identifying every household and listing family members by household. Again, this was a process of collaboration between BRAC staff and community members. Thus, social mapping and census taking were also instrumental for advancing community engagement. These three processes—community engagement, social mapping, and census taking—can be valuable strategies for strengthening health programs in urban slum settings of low-income countries.