CalEnviroScreen, California’s mapping tool that quantifies cumulative impacts in communities, has played a pivotal role in advancing environmental justice in the state. The tool continues to evolve with each version by incorporating new data sources, the latest data, and community involvement and feedback. The tool can be tailored to fit unique applications because the underlying data sets are publicly available. This Comment expands on the points raised in Dr. Charles Lee’s article by sharing lessons learned during the development of the tool and providing insights to other states and jurisdictions as they consider developing mapping tools.