The purpose of this study was to evaluate the dynamics of health and income in contemporary US children and the influence of these dynamics on the age profile of an income–health gradient. Two large cohorts were used to evaluate income gradients in children from 9 months to 5 years and from 6 to 14 years using dynamic specifications of random effects models. An income gradient in parental reports of poor child health was observed in two large cohorts of contemporary US children with ages ranging from infancy to early adolescence. When estimated in separate models both current and averaged income exhibited steepening gradients over the ages of both samples. When estimated jointly only current income exhibited a steepening gradient. While state dependence in health was indicated in dynamic models it did not influence the magnitude or age profile of the income effects. The findings suggested that the age profile of an income–health gradient in the health of US children may depend on whether income is measured as a long-term or short-term variable. Distinguishing these patterns is important for an understanding of how families cope with their children’s health adversities.