Historiometry is one of the oldest methods in personality and social psychology. In fact, the first professional publication in experimental social psychology also incorporated a historiometric study. The present review article begins by describing the nature of the technique with respect to unit definition and sampling, the several approaches to measuring variables, and the correlational nature of the statistical analyses. This description also pinpoints some of the unique characteristics of the approach. These attributes and other attributes are then illustrated using the historiometric research on assessed leadership of US presidents. This research has converged on a single predictive equation that has been successfully replicated and extended over a quarter century of research. The article closes with a brief evaluation of historiometry's future prospects in the field.