This report describes how the Minnesota Head Start community set out to describe the developmental progress of four-year-olds enrolled in Head Start across Minnesota using their research-based child assessment data. The exercise of aggregating data from diverse, locally-controlled Head Start programs offers many important lessons about building a state early childhood data system and establishing data variables that offer meaningful insights into the complex interactions that impact children's early developmental progress. It also contributes to the discussion about how children enrolled in Head Start make progress in essential developmental domains. (author abstract)