Monitoring the well-being of children and adolescents is essential for improving overall population health. However, with only a few exceptions, direct measures of well-being are not currently collected at scale in the United States. Multidimensional indices of outcome indicators related to well-being have been proposed as an alternative, but existing indices have several weaknesses. This dissertation implements a novel methodology to derive an improved index of the outcome indicators of child and adolescent well-being that can be applied to existing population data. Using a nationally representative longitudinal panel, model selection and regression techniques are implemented to estimate the relationship between a collection of standard outcome indicators of well-being with several subjective scales collected directly from children and adolescents. This process results in an index methodology based on their actual lived experiences, making it a more child-centric measure. Within the panel, higher scores on the index are associated with improved health and higher earnings in young adulthood. When subsequently applying the methodology to population macrodata from 2000 to 2019, we find that the outcome indicators of child and adolescent well-being, as measured by the index, improved consistently throughout the past two decades. This overall advance was accompanied by some convergence in disparities by geography and race/ethnicity, but significant inequities remain. However, the progress exhibited by the outcome indicators of well-being contrasts sharply with recent declines in other measures of child and adolescent mental health. This contradiction suggests that the outcome indicators, which at one point tracked reasonably well alongside the subjective well-being of children and adolescents, are no longer performing as expected. Researchers, policymakers, advocates, and practitioners should therefore collectively recommit to expanding population health monitoring systems to better capture the most essential aspects of child and adolescent well-being.