The importance of factual political knowledge in affecting information processing and political behavior has recently received considerable attention. However, relatively little is known about the dynamics of such knowledge over long periods of time. This article utilizes a national two-generation, threewave panel study stretching from 1965 to 1982 to address the issue of dynamics at both the aggregate and individual level. Factual knowledge is divided into the domains of governmental mechanics (textbook knowledge), current events (surveillance knowledge), and historical facts (treated here under the rubric of collective memories). Comparison of the two generations shows that high aggregate continuity sets in by the early stages of midlife, with the young generation showing sharp losses of textbook knowledge but gains in other types. Distinctive generational differences appear with respect to certain events occurring at early, formative life stages. The size of the generation gap depends on time of birth as well as time of observation. Individual-level continuity for mature adults rivals that occurring for strongly held attitudes. Trends within the younger generation indicate the same kind of crystallization process that marks many political attitudes. In view of the high degree of individual-and aggregate-level stability among mature adults, special attention rests on the content of the knowledge that is being hardened and internalized during the early adult years.