Early childhood systems cannot pursue strategic financing, cost modeling, or rate reform without integrated, decision-ready data. This brief, the first in a series on Early Childhood Integrated Data Systems (ECIDS) co-authored by the Center for Early Learning Funding Equity (CELFE) and the Chicago Early Childhood Integrated Data System (CECIDS), explores how ECIDS serves as foundational public infrastructure for early childhood systems. By connecting funding, service delivery, and regulatory data across programs and agencies, ECIDS enables more transparent, repeatable, and data-informed policymaking to support strategic financing, resource allocation, and long-term system planning.