Abstract This empirical study measures the influence of 99 retired Supreme Court justices, analyzing over 1.2 million citations to over 24,000 opinions of the Court written between 1793 and 1991. It models the appointment process as the selection of a capital investment, treating a justice's output as the precedents generated each term and using citations as a proxy for an opinion's value. This model is applied to the retired justices and their opinions, and its consistency is tested by independently analyzing citations by subsequent Supreme Court and circuit court opinions. Influence values also demonstrably track the results of a well‐known survey of judicial greatness. The study challenges several common assumptions. Older appointees have been no less influential than young appointees, and, on an annual basis, older appointees have actually been more influential. Private attorneys have made the most influential appointees, and former judges show no special advantages.