Substate estimates for 15 measures of substance use and mental illness based on the combined 2021, 2022, and 2023 National Surveys on Drug Use and Health (NSDUHs) are provided. NSDUH is an ongoing survey of the civilian, noninstitutionalized population of the United States aged 12 years or older. Estimates presented here are based on a small area estimation (SAE) methodology in which substate-level NSDUH data are combined with county and census block group/tract-level data from the state.