Running parallel to mainstream research on the psychometric assessment of intelligence is another tradition of research on the historiometric assessment of intelligence and closely affiliated variables. Historiometric assessment is based on four data sources: (a) personality sketches (e.g., Intellectual Brilliance), (b) developmental histories (e.g., IQ), (c) content analyses (e.g., integrative complexity), and (d) expert surveys (e.g., Openness to Experience). The first two represent major lines of intelligence research that involved key figures in the development of corresponding psychometric methods (e.g., Galton, Terman, and Thorndike), whereas the last two constitute independent research paradigms that later intersected with the first two. The literature on U.S. presidents then provides an integrated illustration of the four historiometric approaches and how they converge on the same broad conclusions. Significantly, historiometric investigations on the relation between broadly defined intelligence and adulthood achievement obtain about the same effect size as that found in psychometric research (i.e., rs or βs = .25 ± .10). Because historiometric and psychometric studies have rather distinctive methodological advantages and disadvantages, this consistent outcome provides corroborative support for both sets of empirical findings.