Can a diverse crowd of individuals whose interests focus on distinct issues related to racial identity, class, gender, and sexuality mobilize around a shared issue? If so, how does this process work in practice? To date, limited research has explored intersectionality as a mobilization tool for social movements. This paper unpacks how intersectionality influences the constituencies represented in one of the largest protests ever observed in the United States: the Women's March on Washington in January 2017. Analyzing a data set collected from a random sample of participants, we explore how social identities influenced participation in the Women's March. Our analysis demonstrates how individuals' motivations to participate represented an intersectional set of issues and how coalitions of issues emerge. We conclude by discussing how these coalitions enable us to understand and predict the future of the anti-Trump resistance.