Anthropometric data from children are important for product design and the promulgation of safety standards. The last major detailed study of child anthropometry in the USA was conducted more than 30 years ago. Subsequent demographic changes and the increased prevalence of overweight and obesity render those data increasingly obsolete. A new, large-scale anthropometric survey is needed. As an interim step, a new anthropometric synthesis technique was used to create a virtual population of modern children, each described by 84 anthropometric measures. A subset of these data was validated against limited modern data. Comparisons with data from the 1970s showed significant changes in measures of width and circumference of the torso, arms and legs. Measures of length and measurements of the head, face, hands and feet exhibited little change. The new virtual population provides guidance for a comprehensive child anthropometry survey and could improve safety and accommodation in product design. Practitioner Summary: This research reviews the inadequacies of available sources of US child anthropometry as a result of the rise in the rates of overweight and obesity. A new synthesised database of detailed modern child anthropometry was created and validated. The results quantify changes in US child body dimensions since the 1970s.