As patterns of union formation and dissolution in adult lives become complex, the living arrangements of American children are becoming increasingly fluid. With a sample (N = 12,843) drawn from the National Longitudinal Study of Adolescent Health, this study attempted to capture this complexity by mapping out children's family structure histories across their early life course, investigating the implications of these arrangements for their general adjustment, and finally, identifying family processes that explained these associations. The findings suggest that a sizable minority of young people experience dynamic family structure arrangements. Moreover, family structure at adolescence best predicted later emotional distress, and family structure at adolescence plus an indicator of cumulative family instability across childhood best predicted current marijuana use. More so than indicators tapping social control, levels of family connectedness and parent-adolescent relationship quality were key conduits for these associations. (Contains 6 tables.)