We make five over-time comparisons of student knowledge of civics and government: a) knowledge among 4th, 8th, and 11/12th graders between 1975/6 and 1998 using two separate NAEP trend assessments; b) knowledge over the same period by comparing responses to individual items asked in the 1975/6 and 1981/2 assessments to responses on identical questions asked in the 1988-98 assessments; c) knowledge among 12th graders in the 1930s-1960s compared to 1988-98 using a small set of identical or highly similar items; d) the ability of students in the 1950s-1960s versus 1998 to interpret political cartoons and to read tables and graphs; and e) knowledge of current and past high school students on putative "domains" of civic knowledge. In the two older grades, there has been a decline in civic knowledge in the past quarter century. The decline among 12th graders was small, on the order of several percentage points; yet it may have left high school seniors in 1998 able to answer questions only a little better than 8th graders in the mid-1970s. The long-term comparisons suggest that student skills have improved and, more ambiguously, that contemporary high school seniors are not demonstrably less informed about politics and government than were students in the distant past. (Contains 4 tables.)