States around the country are developing unified early childhood data systems--systems that link child, personnel, and provider data across multiple programs--and linking those systems to P-20W statewide longitudinal data systems in order to conduct longitudinal analysis. These next-generation data systems are intended to provide the information policymakers need to improve policy; practitioners need to improve practice; and parents/caregivers need to better take advantage of resources available to their children. In order to build useful systems, states must start with a vision for how they would like the system to be used and, more specifically, a list of essential questions to be answered using the data. In a series of calls sponsored by the Statewide Longitudinal Data Systems (SLDS) Grant Program, state representatives shared experiences and offered tips for sharing early childhood data. A product of these conversations, Answering Key Questions With an Early Childhood Data System is designed to support states working to create or evaluate their current policy questions. This document examines examples of policy questions from states and outlines why those questions are needed, how to create them, and who should be involved in the process. (author abstract)