With their broad service portfolio, strict regulations, and often scarce resources, municipalities face specific requirements and challenges for mastering digital transformation. While maturity assessments have become a common means of improving project management at the organizational level, there is no domain-specific approach yet that focuses on digital project management in municipalities. This article reports on the development and evaluation of ECoProMD, an Easy Communal Project Maturity model for Digitalization. Based on an extended understanding of maturity models as a combination of model and method, we used situational method engineering to design and validate the ECoProMD artifact. A literature review and 19 interviews with seven municipal experts from Germany provided the knowledge base for this research.