In 1965, Daniel Patrick Moynihan warned that nonmarital childbearing and marital dissolution were undermining the progress of African Americans. The author argues that what Moynihan identified as a race-specific problem in the 1960s has now become a class-based phenomena as well. Using data from a new birth cohort study, the author shows that unmarried parents come from much more disadvantaged populations than married parents. The author further argues that nonmarital childbearing reproduces class and racial disparities through its association with partnership instability and multipartnered fertility. These processes increase maternal stress and mental health problems, reduce the quality of mothers' parenting, reduce paternal investments, and ultimately lead to poor outcomes in children. Finally, by spreading fathers' contributions across multiple households, partnership instability and multipartnered fertility undermine the importance of individual fathers' contributions of time and money, which is likely to affect the future marriage expectations of both sons and daughters.