Increasingly, scholars have examined the antecedents and consequences of corporate responses to systemic racism in the United States. We extend research on this topic by theorizing how historical legacies associated with this sociopolitical issue affect firms’ engagement in corporate sociopolitical activism (SPA). Through an analysis of firms’ responses to the Black Lives Matter (BLM) movement in 2020, we find that firms headquartered in counties with strong ties to the historical institution of slavery were less likely to engage in SPA following the murder of George Floyd in Minneapolis, MN. Moreover, even when firms that were headquartered in such counties engaged in SPA, they were less likely to engage in substantive SPA, particularly in forming collaborative relationships with nongovernmental organizations advocating for racial justice. This study contributes to research on corporate responses to racism by showing not only whether institutional slavery affected firms’ responses but also how it shaped the types of responses that firms selected—a choice that has been overlooked in corporate SPA research. Moreover, this paper answers recent calls to show how history affects organizational outcomes.