SUMMARY Adverse childhood experiences (ACEs) can increase the risk for obesity both during childhood and later in adulthood. Emerging evidence suggests a parent's history of ACEs can increase their child's obesity risk, regardless of whether the child experiences their own ACEs. The association between a parent's ACEs and their child's obesity is believed to be moderated by via enduring stress-related effects of ACEs on parent's biology and behavior and family functioning. Research on ACEs-obesity associations rarely focuses on neighborhood environment, yet neighborhood characteristics are relevant to both ACEs and obesity risk. Neighborhood characteristics such as greenspace and food access can impact engagement in obesity related behaviors. Neighborhood factors such as neighborhood poverty and crime can be a source of adversity. Our previous research documented that adults with a history of ACEs live in less health-promoting neighborhoods with more obesogenic qualities (e.g., worse supermarket access, less greenspace). However neighborhood's impact on associations between a parent's ACEs and their child's obesity has not been widely investigated. Illuminating the role of neighborhood requires advanced spatial analytic methods, because neighborhoods are complex environments comprised of numerous synergistic characteristics that co-occur within a broader context of racial and economic segregation. To begin to illuminate neighborhood influences on ACEs-obesity associations, we validated spatial analytic methods for creating a Neighborhood ACEs Index (NAI). A NAI is a weighted composite that answers the question “what is the neighborhood environment of individuals who have experienced ACEs?” It serves as a single-item individual-level proxy for collective neighborhood environment associated with ACEs. Individuals who live in neighborhoods that have more characteristics associated with ACEs have a higher NAI score. Using geocoding and spatial methods, a NAI connects individual-level ACEs data with rich spatial data that includes numerous neighborhood characteristics such as crime, poverty, and healthcare access. A NAI can be used as an independent variable in analyses to examine how neighborhood characteristics associated with ACEs influence the relationship of ACEs and obesity. In addition, a NAI identifies population-specific neighborhood-level targets for interventions and polices. Neighborhoods whose residents have the highest NAI score can be prioritized for trauma-informed obesity reduction efforts. Building upon our prior work, this study will create a NAI based upon parent ACEs and test how that NAI influences associations between a parent's history of ACEs and their child's obesity. We will harness robust existing data from the H2O study (N=1320) that captured parent ACEs and child obesity, rich spatial data that captured neighborhood environment, and robust spatial methods. Collectively, this study is a foundational step towards our long-t...