This work is part of a larger AI/AN Early Childhood Needs Assessment design project (AI/AN EC Needs Assessment), conducted for the Office of Planning, Research and Evaluation within the Administration for Children and Families (ACF), in the U.S. Department of Health and Human Services. As part of the design project, Mathematica Policy Research convened a Community of Learning (CoL) to inform three design topics on describing the AI/AN population, studying early childhood services organization and delivery, and assessing features to support community capacity for conducting needs assessments, that form the basis for a needs assessment. For more information on the design topics see the design report (Malone et al. 2016).The current report presents the process and findings from implementing Design One―describing the population of AI/AN children and families and their participation in early childhood services based on existing data sources―with a set of national survey and ACF administrative data sources. The current implementation of Design One seeks to address three research questions: (1) What existing data sources could help us understand AI/AN early childhood needs? (2) What information from these sources has been published to date? (3) What can we learn about AI/AN early childhood needs when conducting new analyses by using existing sources? Design One and the AI/AN EC Needs Assessment more broadly are building blocks for conducting an accurate national assessment of the met and unmet need for services for children prenatal to five and their families. The design report, reflecting discussions with the CoL, identified 87 key indicators across 9 research questions for Design One to address, and identified 21 data sources with potential to address them. In this report, we focus on six of these data sources—two national survey data sources from the U.S. Census Bureau and four administrative data sources on grantees funded by ACF. These data sources were reviewed and a subset analyzed to see if any could provide information on the key indicators within each research question, thereby meeting Design One’s aim to paint a portrait of need at the national level, using existing data.