In 2015, the Old Fadama slum of Accra, Ghana was a government 'no-go zone' due to the generally lawless environment. Participatory action researchers (PAR) began working with three stakeholders to resolve complex challenges facing the community and city. In three years, they created a PAR cross-sector collaboration intervention incorporating data from 300 research participants working on sanitation. In 2018–2019, the stakeholders addressed the next priorities: community violence, solid waste, and a health clinic. The PAR intervention was replicated, supporting kayayei (women head porters) in Old Fadama, the Madina slum of Accra and four rural communities in northern Ghana. The process expanded, involving 2,400 stakeholders and an additional 2,048 beneficiaries. Cross-sector collaboration worked where other, more traditional development interventions did not. This PAR intervention provides developing-country governments with a solution for complex challenges: a low-cost, locally-designed tool that dramatically improved participation and resulted in projects that impact the public good. This title is available as Open Access on Cambridge Core.