No single U.S. health surveillance system adequately describes the health of people with intellectual and developmental disabilities (IDD). Researchers and policy makers have sought to understand the potential of state and local administrative and survey data to produce a local as well as a national picture of the health of the population with IDD. Analyses of these secondary data sources have significant appeal because of the potential to derive new information without the burden and expense of new data collection. The authors examined the potential for data collected by states and territories to inform health surveillance in the population with IDD, including data from the administration of eligibility-based supports, health insurance claims, and surveys administered for monitoring and quality improvement. Although there are opportunities to align and harmonize datasets to enhance the available information, there is no simple path to use state and local data to assess and report on the health of the population with IDD. Recommendations for policy, practice, and research include the development and use of consistent operational definitions in data collection, and research to fill knowledge gaps.