U.S. "child marriage"-marriage including at least one person under the age of 18-is legal and practiced in 44 states. In this article, I map the existing literature on child marriage and offer insights on how child marriage can expand our sociological understandings of marriage, gender inequality, and youth sexualities. Social scientists have almost exclusively focused on child marriage in the Global South at the expense of understanding child marriage in the Global North, which I argue reinforces racist and xenophobic narratives that cast child marriage as a non-Western social problem. The research on U.S. child marriage that does exist focuses on the consequences, rather than the causes, of child marriage, which may shift focus away from a structural understanding of how intersecting inequalities shape girls' likelihood of getting married as minors. I position a sociology of U.S. child marriage at the intersection of sociological understandings of marriage and gender inequality and critical research on youth sexualities. I conclude by calling for intersectional research on U.S. child marriage that builds on these literatures, examining how girls' sexualities are racialized, gendered, and classed within the institution of marriage.