Environmental justice research increasingly recognizes the need to bridge community knowledge with spatial technologies to document and address place-based inequities. This study explores how Participatory GIS (PGIS) serves as a platform for integrating diverse lived experiences into environmental decision-making. Over the course of a year, our research team facilitated four seasonal workshops in Nogojiwanong/Peterborough, Ontario, where racialized, Indigenous, and working-class residents collectively mapped environmental harms and benefits. Through digital mapping and group discussions, participants not only documented their experiences but also contributed to a broader understanding of how environmental injustices are spatially distributed. This research examines the tensions and opportunities of using GIS within a Participatory Action Research (PAR) framework, particularly in challenging traditional power structures in cartography. While GIS has often been critiqued for its inaccessibility, our findings highlight how co-producing spatial knowledge can foster collaboration and inform policy interventions. By combining qualitative insights with spatial representation, this study demonstrates how participatory mapping can bridge disciplinary divides, strengthen community agency, and provide new pathways for addressing environmental inequities. This work contributes to discussions on the intersections of cartography, environmental justice, and participatory research, emphasizing the role of mapping in bringing together diverse perspectives for meaningful action.