We investigate the effect of the anniversary commemorations of September 11 and Woodstock on the American public’s collective memory or collective knowledge of each event. We are able to examine both the eighth- and the tenth-anniversary commemorations of the September 11 attacks (in 2009 and 2011), as well as the fortieth anniversary of the 1969 Woodstock Festival (in 2009). In an initial step, we used media analysis to identify the timing of commemorative activity surrounding the anniversaries. Our second step was to draw on data from surveys whose fieldwork dates corresponded to the anniversary periods, in order to compare respondents’ memory and knowledge of the events before, during, and after the commemorations. Our evidence shows that the percentage of Americans who consider 9/11 an “especially important” event is related to commemorative activity, and we likewise find that greater knowledge about the Woodstock Festival is associated with commemoration of that event. In addition, the impact of commemoration on knowledge of Woodstock was greatest among those with lower levels of education. For memory of 9/11, we found that commemoration’s effects were stronger for blacks than for whites, suggesting that commemoration may enhance the salience of national, as opposed to racial, identity. These findings offer insights into the educative and evocative roles of commemoration.