Sociologists have long been interested in collective representations of the past, as well as the processes through which individuals, groups, or events have been excluded from those representations. Despite this rich body of literature, few studies have examined the processes through which long‐silenced countermemory becomes integrated within “official” public memory. This study examines two instances of silence breaking in Philadelphia, Mississippi—the town notorious for the silence, denial, and collective obstruction of justice surrounding the 1964 “Mississippi Burning” murders. By reconstructing and comparing the event structure of the twenty‐fifth and fortieth anniversary commemorations—both interracial community‐wide events unique for having punctuated Philadelphia's prevailing silence on the murders—this article finds that commemorability and mnemonic capacity are necessary but insufficient factors for “silence breaking” commemorations to emerge. This study identifies two additional criteria necessary for commemorations that publicly acknowledged long‐silenced pasts: pressure from external forces, and the convergence of interests between those previously opposed to and those in favor of acknowledgment.