Scholars theorize that "opportunity gaps" drive achievement disparities between children born into poverty versus affluence. In a 26-year longitudinal study (N = 814), we examine (a) economic disparity in children's accumulation of opportunities--from birth through high school--at home, childcare, school, afterschool, and in the neighborhood; (b) the extent to which opportunity is linked with educational attainment and earnings in early adulthood; and (c) whether opportunity is most strongly associated with these adult outcomes for children from low-income households. We document large opportunity gaps between children from low- versus higher-income households. These opportunity gaps are strongly linked with educational attainment and earnings, particularly for low-income children, helping explain why household income in early childhood predicts these outcomes in adulthood.