Between 1972 and 1978 U.S. high schools rapidly increased their female athletic participation rates in order to comply with Title IX. This paper examines the causal implications of this expansion by using variation in the level of boys' athletic participation across states before Title IX to instrument for change in girls' athletic participation. Analysis of differences in outcomes across states in changes between pre- and postcohorts reveals that a 10 percentage point rise in state-level female sports participation generates a 1 percentage point increase in female college attendance and a 1 to 2 percentage point rise in female labor force participation.